Matthew 'Matt' Daehler is a student at Beacon Hills High School, an amateur photographer and a member of the Cyclones lacrosse team. Prior to the series, in 2006, Matt almost drowned at a pool party held by Mr. Lahey and the beacon Hills high school swim team, to his trauma and humiliation. In Season 2, Matt Daehler is a psychological stalker who fixates on Allison Argent and becomes the master of the kanima, enslaving Jackson Whittemore after the latter is cursed as a kanima. He takes command of the shapeshifter, goes on a killing spree, killing Mr. Lahey and all former high school students who were involved in his near drowning and becomes a hidden foe of Scott McCall, Stiles Stilinski, Allison and Derek's Pack. Matt is eventually exposed as the kanima's master and the killer, but takes Scott, Stiles, Derek Hale, Melissa McCall and the sheriff hostage. He menaces them, and confesses everything to Scott, his motive and all his experiences with the kanima. During the skirmish between all parties involved, Matt slips away, then is assaulted then killed by Gerard Argent.
Matt presents himself as a friendly, easy-going, cocky and confident everyday high school student.
Underneath his self-perceived view of being a well-adjusted teenager however, Matt is in truth callous, psychotic and unhinged. He displayed all the traits of a typical stalker, obsessive, perverted and intrusive. He inappropriately pursued Allison by inconspicuously taking photoshots of her from everywhere without her consent. When he suspected Jackson was making a sex tape under the misinterpretation that it was for Allison to see, he proved to be a peeping tom, by remotely accessing the camera and viewing Jackson's video for himself. He also photoshopped himself into many of his candid shots of her, deluding himself into thinking he and Allison were in a romantic relationship.
As a result of his childhood trauma and keeping it secret for years, Matt's psyche is extremely damaged to the point of him becoming a murderer. He is self-righteous, aggressive, irrational and demented. He persistently justified his murderous actions that the swim team 'murdered' him, reflecting on his near-death experience, that because of their role in causing his trauma, they were in debt to him. Matt's self-absorbed dementia was so far that he displayed no consequences in taking Scott, Stiles and their parents hostage.
During his death, Matt died in terror and emotional pain, flashing back to his near-drowning.
When Matt was 9 years old, in 2006, he went to the Isaac Lahey's house to make a first edition comic book trade with Isaac.
Matt started to drown, swallowing water. He cried out for help, but everyone just drunkenly laughed. As Matt went under, he saw Camden and Bennett swimming, Sean and Jessica feeling each other up as well as Tucker and Kara. Matt drowned, and noticed that the light everyone always says you see when you die didn't exist, just darkness.
Matt was rescued and resuscitated by Mr. Lahey. The coach berates Matt that his near-death experience was his own fault, because "what little bastard doesn't know how to swim." Lahey demanded that Matt say nothing, that he tell no one about what happened so no one finds out he let teenagers drink alcohol.
Matt obeyed keeping the incident secret. He caused himself trauma in the seven years that followed. He had nightmares where he's drowning and he would wake up gasping for breath. His parents thought Matt was asthmatic and even brought him an inhaler.
Matt is at his locker at the high school. Allison Argent's locker is just a few down from his. On the day of her aunt's funeral, he sees her take her dress out for the event. Matt compliments Allison on her dress. She compliments his camera in return. He flashes her a smile, just before two female students behind them gossip about Kate's murder spree, upsetting Allison.
Taking his photos, Matt starts when Mr. Lahey gets in one of the shots. Remembering his near-drownng at Lahey's house seven years ago, Matt looks down the lense of his camera. Suddenly Matt feels an unbelievable rage towards Lahey filing up inside him+.
Matt: (thinking) "I WANT TO SEE HIM DEAD."
Gerard Argent then appears behind Matt and accosts him, snatching the camera from Matt. Matt warns the elderly man the camera cost $900. Gerard takes out the SD card and snidely asks how much the card was worth and snaps it in half. Matt, pissed, leaves the funeral.
The next day, Matt is amazed, astonished once he finds out Lahey is dead+.
At lacrosse practise a few days later, Jackson Whittemore asks Matt to lend him a digital video camera. He asks Matt for something that works well in low light and would record all night long. Matt is suspiciously as to why Jackson needs a camera to record "all night long". He asks Jackson does he have a $100. Jackson smugly replies he drives a Porsche.
Matt thinks Jackson using the camera to make a sex tape and asks is it about Allison as he say the two of them at the school formal a couple of weeks ago, thinking he's making a sex tape for Allison to see. Jackson teases Matt realising he has a crush on Allison and is insulted that Matt thinks he'd do anything so ordinary as making a sex tape. Jackson sharply replies he's documenting "(his) history" which puts Matt off. Jackson brusque Lydia takes the camera from Matt saying he'll get it back tomorrow. Matt relents and walks down the lane from Jackson's house. Matt resolutely looks back at the Whittemore's house. He sees flashlights in the coronered off Lahey house across the street.
Returning to his car, Matt takes out his phone and pulls up an app that remotely accesses the video camera he just lent Jackson. Matt spies on Jackson as the camera films the latter just lying in bed. He curses Jackson and continues to spy. As the time goes by, Matt starts to fall asleep. He jerks awake. Going back to look at his phone, Matt sees Jackson there fast asleep.
Matt perks up, curious when Jackson wakes up, but rises from his bed as if he's possessed.
Matt: "What the hell??"
Matt then freaks out as he sees Jackson transforming. First, the boy's eyes glow yellow, then his shape morphs, transforming into a shifters. Matt is overwhelmed with disbelief and horror seeing Jackson as a serpentine-like monster.
Suddenly, Matt feels a change within him. He hears and starts to sense the creature he's seeing first on his video camera app leave the Whittemore residence and is approaching him in his car. He then starts to feel empowered; he feels instinctively drawn towards the monster as if it's natural. Matt then sees the fully shifted creature in his side view mirror. He sheds a tear in confusion, but instead of feeling afraid, he continually feels drawn towards the shapeshifter as it walks up to his car's left side door.
Matt suddenly sees a vision: he's sees Mr. Lahey. The man Matt has hated all his life is running in fear from something. Lahey's running from the creature Matt is seeing. The vision continues with the creature chasing Lahey into his car, the creature ripping off the front door and savaging Lahey, clawing him apart inside the car, killing him.
Matt snaps out of the vision. He realizes the creature is Jackson, that the vision he saw was the creature's memory and it had killed Lahey for Matt himself. He now feels avenged for the trauma he's suffered for the incident when he nearly drowned.
Matt realizes that some supernatural bond has been forged between himself and the creature. He soon becomes aware of the power he has over the creature. He instinctively starts to develop this new power the creature gives him. He is able to control, command it and he can mentally project himself through the shapeshifter's view+++.
After forging it's bond with Matt, the shapeshifter breaks into Isaac's house for Matt to investigate the flashlights Matt saw earlier. Matt is aware as the creature menaces a shapeshifted Scott McCall and Allison inside.
Like the rage he felt towards Lahey, he feels furious, vengeful towards the swim team members who he saw having fun in the pool, fooling around, drinking while he was drowning, dying.
He decides to kill them all to get back at the team's members. Matt knows now that Jackson will kill for him again.
Once the shapeshifter transforms back into Jackson. Matt arranges to have Jackson back into his bed to make it appear that nothing out of the ordinary happened. Donning gloves, he also modifies the video on the video camera to remove the two hours of footage where Jackson had shapeshifted and was missing from his room.
A couple of nights later, Allison is at a gas station to fill up her car. Matt is stalking her from a distance, unseen. Matt suddenly sees the only occupant at the station, besides Allison. He recognizes him as Bennett, one of the swim team he remembers. Feeling similarly vengeful feelings as towards Lahey,
At the end of the week, Jackson returns the camera, but it has a cracked lens. Matt yells at him for it in Biology, but Jackson ignores him in favor of watching the video on immunity, snapping at Matt to send him a bill.
Matt, knowing that Lahey and Bennett are now both dead, fanatically wants more payback. He goes to Tucker Cornish's garage for his car. He pays Tucker for an oil change. He is insulted at Tucker not knowing who he is. In Tucker's blind spot, Matt snaps a picture.
Later that night, Matt finds out Tucker is dead, knowing Jackson became the creature and had killed him.
Matt now realizes the rules that operate around his bond with the Jackson as the creature: all he has to do is take their picture, then Jackson will take their life, carrying out his vengeance+.
Matt is beginning to use Jackson to spy on Allison, Scott McCall and Stiles Stilinski to find out what they know having become aware they are involved and that Scott is also a shifters. He hears them talk of the bestiary at some point+.
Matt continues to photograph the game. He sees Allison across the field and takes a shot. Melissa McCall notices him taking pictures and asks if he's the yearbook photographer.
Matt: "No. I ... I just take pictures."
Melissa: "Just lacrosse or other things?"
Matt: (Gazing fondly at a shot of Allison) "Anything that catches my eye."
Moments after the game, Matt has Jackson transform and follow Stiles to the school's pool. Again, using his psychic link to Jackson to command the shapeshifter, Matt has Jackson menace, then attack Stiles, Derek Hale and the latter's Beta.
When Stiles and Derek become stranded in the pool, the shapeshifter absorbs Matt's aquaphobia. Once the incident at the pool passes, Matt has Jackson's memory modified so to have him remember that he went home right after the game.
Matt meets with Danny again during break. He scrolls through the photos in his camera and realizes that all the ones of Scott McCall have bad lens flare, to his confusion. He knows it's because Scott is somehow different as part of the supernatural monster business he's now a part of. Suddenly, Isaac Lahey and Erica Reyes appear beside them. Isaac grabs Matt by the shoulder demanding to knoow where Lydia is, to Matt's confusion
When Matt runs into Scott in the hallway, he calls his name to make Scott turn and snaps another up close photo of him, which has the same problem centred around eyes. Matt stares after Scott curiously.
Matt is nearby during the confrontation between Scott's friends and Derek's Pack at Scott's house. He's arrived in Mr. Adrian Harris stolen car and taking care of his fingerprints by wearing gloves. He has Jackson transform. He then calls the shapeshifter to him.
As a shapeshifted Jackson races throughout Beacon Hills for Danny, Matt keeps to shadows as his servant is being pursued by Derek Hale, Scott and the Argent hunters. When Jackson is disabled by Derek at Jungle, then captured and held hostage by Scott and Stiles in a stolen prison transport van, Matt locates the restored video in the back of Danny's car and recovers it, while continuing to spy on Scott and everyone around.
The following night, Matt has tracked down two more members of the swim team he remembers, Sean and Jessica who are living together outside of town in a trailer. He has Jackson transform again and has him escape the prison van+.
The trailer suffers an electrical breakdown and Sean comes out to repair the generator. Matt takes the opportunity to walk right up to Sean getting in his face. Sean talks back to the teenager. But Matt points his finger up to above the two of them. Up in the trees, Jackson, at Matt's behest attacks wrapping his reptilian tail around Sean's neck and lifts the young man right into the air and strangles him.
Satisfied, Matt then directs the shapeshifter towards the trailer where Jessica is staring in horror, ordering her to be killed next. The shapeshifter tosses Sean's corpse through the trailer's window to terrify Jessica. Jackson then moves in to kill the woman, until he sees that she is heavily pregnant. Matt and Jackson leave, sparing Jessica for the time being.
The next day at school, Matt continues to spy on Scott's friends. Matt runs into Allison as she's trying to find Jackson in the boys locker room. He notices that she's walking around without her high heels on and cracks a joke about how his heels hurt his feet too. He then asks her if she'd like to go to a rave party for the Underground Shell on Friday with him, and a distracted Allison offhandedly agrees. Matt's excited that he's getting to take Allison out on a date.
Matt: (Psychically controlling Jackson and speaking through his mouth)
Allison: (nervously) "I - I - I have to get to class."
Matt: (laughing) "No. No. No. You don't. Not when you have perfect grades. You can skip one class."
Matt then insults her, Scott and their secret "Romeo-And-Juliet" relationship, attempting to force Allison to break up with Scott, his words coming through an unaware Jackson's mouth. Allison snaps and fights back against Jackson. Matt's link to Jackson is broken, and the latter then returns to his normal self.
Matt then comes back to the boys' locker, just in time to see Scott and Jackson fighting. Matt sees Allison's tablet with the pages from the bestiary and emails himself a copy without anyone noticing. Matt then ends up getting sent to detention along with everyone else. At detention, he sits next to Allison and keeps muttering "kanima" to himself as he reads Lydia Martin's translation of the text. Matt realizes Jackson is what Scott's friends are calling a 'kanima' and Matt himself is his master.
Mr. Harris then tells them that they have to put away all the library books before they can leave, while he goes home himself. Matt is in the same aisle as Jackson while they work. As they put away books, Matt has Jackson shapeshift into the kanima. He slices Matt on the back of the neck, paralyzing him, to throw suspicion off of him and then Jackson destroys the library.
Matt: "Stay out of my way, or I'll kill all of you."
The kanima then escapes out the window, Allison leans over Matt and says she has to get him to the hospital.
Matt is taken then to the hospital. He knows Jessica is also at the hospital, her having given birth to her baby.
He runs into Melissa McCall who complains about the dirt his footprints are leaving+. Matt finds Jessica, entering her hospital room. He dons his perp gloves and as Jessica wakes up, he grabs her over her mouth and smothers her to death, murdering her. Following his plan to frame Adrian Harris, he again leaves tire tracks from Harris' car closeto the crime scene+.
While spying on Scott and continuing to stalk Allison, Matt photographs Allison relenetlessly, and starts photoshopping himself into his shots. In his forged photos, he and Allison are depicted as a couple with them kissing or holding hands+.
Matt puts on an act, nervously asks if Jackson is going to hit him again. He lets Jackson cut in line, even though Jackson hasn't said anything. Scott then shows up and asks Matt how much tickets are. Matt tells him $75, and Scott asks to borrow $75. Matt gives Scott a look like he's crazy. He ends up not able to buy any tickets because the seller gets freaked out and leaves.
At the end of the week, Matt asks Scott and Stiles why no one is getting in trouble for what happened in the library. Stiles tells him that nobody got hurt, but Matt points out that he was in the ER with a concussion. Stiles doesn't care at all, but Scott asks if Matt's okay. They then talk about that night's rave. Matt was able to get tickets online and encourages them to keep trying.
However, as Jackson is again moving in towards Kara Simmons, with pluck, the werewolves manage to subdue Jackson. A distracted Matt tries to get her to have a good time and asks if she'd like to move closer to the DJ. She follows him, and they bump into Mr. Harris, who is out with a much younger date. Eventually, they take a seat off the dance floor.
Isaac, Erica and Stiles hold a subdued Jackson in a separate room. Stiles hopes that Jackson's puppeteer decided not to show up, but Matt then fully possesses his servant and snaps at Stiles he's right in there with them.
Stiles: "Well who did they murder?"
Matt: "Me. ... They murdered me. They murdered me!"
Matt then has Jackson begin to shift. The ketamine they drugged him with is wearing off. He then diverts his attention to Allison. Matt asks Allison if she's okay, since he can tell she isn't having a good time. She admits to feeling like she makes one mistake after another. He kisses her, then realizes that wasn't a good idea. She tries to tell him that it's okay, but it isn't. Meanwhile, Jackson then fully shapeshifts into the kanima, and locates Kara Simmons and slits her throat.
At some point, Allison goes back for Matt and drives him home. He apologizes for kissing her, and she tells him not to worry about it. He asks her if she and Scott are still together. She asks if he'd understand if she said it was complicated, and he replies, "Not really." Matt responds he hates "Not reallys", but they both laugh it off. He reassuringly touches her hand and then gets out of the car.
On Wednesday, Matt goes to Lydia's birthday party. Lydia gives a glass of punch to Matt, and then Allison and Matt see each other. She ignores him, and Matt tosses out his drink.
Matt asks Allison for a chance to talk, so she gives him two minutes. He tries to close the door to the bedroom they're in, but she tells him no. He explains that he took some pictures that he probably should have told her about but asks if it's that bad that he thinks she's beautiful. Allison confronts him that she doesn't know how he took some of his photos of her. He responds "tele-photo lens."
Matt: "Come on, Allison. Photographers call them candids."
Allison: "Well police officers call it stalking."
Matt gets angry that she thinks he's the kind of guy who's gonna say something like, "Well if I can't have her, no one can"? He says that another pretty girl will walk through the room in five minutes, so she says he's in luck that he'll only have to wait another three. When she tries to leave, he grabs her arm, and she judo-flips him to the ground.
Matt: "No, no, no!! Don't! I can't swim! I can't-!"
Matt is then thrown into the pool, and he starts panicking and flailing. Jackson immediately pulls him out of the water and helps Matt to his feet. Gasping, he glares at everyone in embarrassment and fury. He sees Scott and Stiles staring at him. Matt, knowing that they've made him as the kanima's master, glares at the two of them and leaves the party.
The cops arrive and everyone takes off. Matt completely loses all sense of restraint. He faces Scott from across the street fuming, with a fully transformed Jackson by his side. They then disappear into the crowd.
Stilinski: "Matt? It's Matt, right? Matt, whatever's going on, I can guarantee you there's a solution that doesn't invole a gun.
Matt: (sarcastically) "You know, it's funny you say that because I don't think you're aware of just how right you are. ... Actually I want to hurt a lot of people."
Off his rocker, Matt offhandedly remarks the three of them weren't on his list, but he can add them. He orders them to all put their phones on the desk. Then he has Stiles cuff the Sheriff onto one of the benches by the cells. Matt leads Scott and Stiles away. He has the two destroy all the evidence that points to him. A car pulls up, and Matt marches the two of them to the front door and has Scott open it, thinking it's Melissa.
Derek: "This is the one controlling (Jackson). This kid?"
Matt: "Well, Derek, not everyone's lucky enough to be a big, bad werewolf."
Matt lets everyone know with glee he's learned all the supernatural phenomenon that's around. Knowing Scott's mom is on her way to make a statement, he has Jackson paralyze Stiles. Matt tells Scott that if he does what he tells him to do neither he nor Jackson will hurt his mother, persuading him by stamping on Stiles' throat. Scott complies.
Matt then locks a horrified Melissa in a cell. He insults Scott over the fact she and Stilinski don't know he's a werewolf.
Matt orders Scott to go back to the front of the station, and there he demands the bestiary. Scott tells him that Gerard is the one who has it. Matt states he needs answers and shows them the skin of his torso, which is beginning to turn into the kanima's hide. He orders Scott to send a message to the Argents. Unbeknownst to Matt, Derek realizes Matt is now transforming into a kanima, because he broke the rules of the being the shapeshifter's master, by murdering innocent people and taking lives himself.
Matt gets Scott alone after Scott heals. Matt comments that Scott's now thinking he'll have to explain how his bullet wound has healed but he doesn't realize how lucky he is that he's healing. Scott asks him if he drowned which gets to Matt.
Matt: "You know Eienstein was right. "Imagination is more important than knowledge." It was like something out of Greek mythology. Like the Furies coming dowm to punish Orestes. ... Jackson is my fury
Suddenly, the lights all go off. The Argent hunters open fire on the building, setting off smoke bombs and storm the sheriff station looking for Derek, Jackson and Matt. In the ensuing skirmish, Derek recovers from the kanima's venom, faces off against the kanima. Matt takes cover and hides, using Jackson to fight off the opposing foes.
Matt kneels next to Allison ordering his servant to hold. He ashamedly tells her she should have given him a chance and again incessantly insists he's not a stalker, one of those guys who says "If I can't have her, no one can"."
Matt: "It's not totally true because ... Allison, ... if I can't have you, NO ONE CAN!"
Before Matt can kill Allison, there's a noise in the distance, and Matt goes to investigate. While he's gone, Chris slips himself and Allison to safety.
Matt angrily knocks out an escaped Stilinski before he can intervene. He menaces Melissa again but a shapeshifted Derek comes up from behind him. Matt just summons Jackson to fight off the werewolf and takes cover again.
Matt runs on to a bridge at the river, the kanima following him. He runs straight into Gerard Argent. The elderly hunter intercepts Matt, throwing him off the bridge, then into the river.
Gerard stands over Matt and holds him down under. Matt struggles, squirms to escape from underneath the psycopath to no use. Soon he's drowning again. Matt desperately looks up in terror, agony at Gerard standing over him, painfully having flashbacks to the party seven years ago including seeing Lahey standing over him, and drowns again. Matt, losing his mastership of Jackson, dies.