How He Left: Unlike the other characters in this gallery, Derek still resides in Beacon Hills, alive and well — though we'll see where he ends up when Teen Wolf returns for Season 5 later this year.
Why He Left: "I want to try new things," Hoechlin told EP Jeff Davis after filming a movie that "scared him." As Davis relayed during the show's PaleyFest panel this week, Hoechlin "wanted to do other things that scared him."
Chance of Returning: Highly likely. Davis said, "We have not seen the last of Derek Hale," adding that he and Hoechlin have met to discuss "possible story lines" for Derek in Season 5.
Keahu Kahauanui as Danny Mahealani
How He Left: Though his exit was ambiguous, Danny hasn't appeared since the Season 3 finale, in which it was revealed he knows about the werewolves.
Why He Left: Neither Kahauanui nor EP Jeff Davis have spoken publicly about this exit.
Chance of Returning: Not likely. During the show's PaleyFest panel in March 2014, Davis simply said, "We'll see" when asked about Danny's return. (And it wasn’t a hopeful “We’ll see.”)
Daniel Sharman as Isaac Lahey
How He Left: Isaac departed from Beacon Hills with Chris Argent at the end of Season 3… and never returned.
Why He Left: "[Sharman] came to me shortly after Crystal [Reed]," EP Jeff Davis told TVLine in March 2014. "We'd actually convinced him to do Season 3B; I think he was holding out on that as well. He told me he wanted to try other things, maybe do a movie."
Chance of Returning: Highly unlikely. Sharman's post-Teen Wolf career is really taking off, with a solid run on The CW's The Originals and a plum role in a CBS medical drama pilot. Frankly, there's nothing left for Isaac in Beacon Hills.
Why She Left: In addition to the cast's age gap — Reed was 29 when Allison died, nearly 10 years Tyler Posey's senior — she said she "wanted to explore other avenues of film and TV." Reed added that EP Jeff Davis wrote her a "great ending."
Chance of Returning: Not entirely impossible, but only in a flashback or dream sequence. Reed hasn't kept too busy since leaving the show, so availability wouldn't be an issue.
Colton Haynes as Jackson Whittemore
How He Left: After finally(?) becoming a werewolf at the end of Season 2, Jackson relocated to London during summer vacation.
Why He Left: Neither Haynes nor EP Jeff Davis have spoken publicly about this decision. Unconfirmed reports claim Haynes' exit was simply a result of failed contract negotiations.
Chance of Returning: Highly unlikely. Just two months after leaving Teen Wolf, Haynes was cast as Roy Harper on The CW's Arrow, where he remains to this very day.