Dr. Alan Deaton, prior to the series, was the emissary and confidante to the evolved alpha werewolf Talia Hale. He harboured romantic feelings for Talia, but retired when the Hale House Fire decimated the Hale family. In Season 1, Alan is the veterinarian of Beacon Hills animal clinic and Scott McCall's employer. Alan learns that Scott has become a werewolf, then treats and saves Scott after the latter is shot with a wolfsbane laced bullet by Kate Argent, revealing to Scott he is aware of the supernatural side of Beacon Hills. In Season 2, Alan assists Scott and Derek's Pack when Jackson Whittemore becomes a kanima and works with Scott to incapacitate Gerard Argent. Afterwards, he and his sister, Marin Morrell work on tracking Gerard down. In Season 3, Alan identifies the new enemy as a darach. He and Marin work with Scott and his friends to fight back against the Alpha Pack and track down the Darach. To save their respective parents, Alan proposes and orchestrates the sacrificial ritual for Scott, Stiles Stilinski and Allison Argent to locate the Nemeton which renews the Nemeton's power. After Scott becoming an alpha, Alan starts to officially serve as an emissary for Scott's Pack. Later, Alan advises the trio on how to resolve the aftereffects of their sacrifice, then works with the pack to exorcise Stiles of a Nogitsune, then to seal the dark kitsune away using the Triskele Urn. In Season 4, Alan sets out to find out what Kate Argent's spell means for Derek. In Season 5, Alan seeks to learn more of the Dread Doctors and their works. He is captured, then held hostage by the Desert Wolf, but is rescued by Malia Tate. Alan is able to save Lydia Martin from death by her trepidation, then when Mason Hewitt is erased from existence replaced by la Bête du Gévaudan, Alan advises and directs the pack to the lore to restore Mason to his true self.
Alan is astute, calm and collected and is a compassionate and dedicated humanitarian and medic. He is shown to be extremely intelligent, calm and collected, and well-versed in the field of the supernatural. As such Alan always steps up to help and treat anyone in need.
Alan is initially rather cryptic, mysterious and withdrawn due to the massacre of the Hale Pack and his love Talia Hale. Nonetheless, he has a sense of duty and honor having watched over Derek having steadfastedly upheld a promise he made to her. Once it is clear Scott and his friends have been drawn into the supernatural world, Alan makes the decision to enter the world of magic and the supernatural again to keep an eye on them.
Alan is a parental and mentor figure, supportive, encouraging, serving as Scott's surrogate father figure, a pillar of faith and hope for the Pack and their allies. Alan holds Scott in high regard as he believed Scott would have the potential to be a True Alpha once he knew Scott had been Bitten. Though Alan is generally calm and collected, he is protective of his sister Marin as shown during the Alpha Pack's reign and in spite of his peaceful mindset he will take actions to defend himself against the more lethal supernatural being.