In Season 4 of Dexter, Dexter meets Arthur Mitchell (John Lithgow), a murderer whose nickname is the Trinity Killer. Dexter befriends him under a false name to understand how Arthur remains a devoted husband and father but still gives in to his urges to kill. Things get a little hairy, however, when Dexter witnesses Arthur being abusive toward his family.

Before Dexter can get rid of Arthur, Arthur finds out Dexter's real name and kills his wife. Dexter eventually kills Arthur, but still loses his wife and the life he had been building for himself outside of being a killer.

Like Jennifer Carpenter's, John Lithgow's return to Dexter might be tricky. Since his character is dead, he could serve as a reminder for viewers and Dexter about the protagonist not being able to run from who he is.