John Mitchell Season 3

When Mitchell enters Purgatory to rescue Annie – following a terminally ill patient at the hospital where George and Nina now work through the Door after his demise -, he learns that the time and date of his death has been confirmed, and he will be killed by a werewolf at some unspecified- but apparently not-too-distant- future date, although he later comments to Annie that he doesn't believe a word of what he heard. Although haunted by both the 'prophecy' of his death and the continued police hunt for the person responsible for the 'Box Tunnel Twenty' massacre, Mitchell rejected an offer to depart Britain to live with the vampire 'Old Ones', commenting during a talk with permanently teenage vampire Adam that his friends help him remain clean as their goodness inspires him by forcing him to think about the disappointment they would feel if he succumbed to his thirst. After a confrontation with vampire 'fan' Graham, Mitchell tried to tell Annie the truth about the tunnel massacre, but Annie simply told him that whatever he had to tell her didn't matter, assuring him that all she wanted was the man he was now and that what he'd done in the past didn't matter compared to what he'd done for her and George, the two subsequently kissing. Although Annie tries to find ways for their relationship to become physical at first, Mitchell admits that he actually prefers their current bond, as sex has always been about violence rather than love with him, and he prefers for his relationship with Annie to be 'pure' and apart from that.

Despite some tension with werewolf vampire-hunter McNair due to Mitchell's concerns regarding the 'prophecy' of his death- although he claims to Annie that he doesn't believe in fate-, Mitchell and McNair reached a certain understanding when they worked together to save George and Nina from a group of vampires, although McNair still feels that Mitchell's sins will catch up to him eventually. When Herrick returns to life, Mitchell initially attempts to stake him- particularly after Cara stakes herself before she can tell Mitchell how she and Daisy brought Herrick back-, but is convinced by George to let Herrick live on the grounds that he deserves the same chances everyone has given Mitchell. When Annie learns about Mitchell's role in the massacre, she tearfully convinced him to allow himself to be arrested, Mitchell going along with it to prove his love for her even as he tries to escape being processed due to the risks if his true nature is exposed.

Although Herrick released Mitchell- revealing in the process that his resurrection was aided by the fact that he was torn apart rather than just being staked-, Mitchell finally staked Herrick when he concluded that he had seen and done enough in his life. With the news that another man had been framed for the Box Tunnel Twenty he returned to the house to ask George to kill him, recognising that whoever had set up that frame would want a favour later and wanting to free his friends of the taint he had brought to their lives. He is then killed by George, after The Old Ones' attempt to use Mitchell to do their dirty work (work spelled out by old one Wyndham). George's last words to Mitchell are: "I'm doing this because I love you", to which Mitchell responds "I know".