Dr. Terence Wynn is one of the doctors at Smith's Grove.

His first appearance is in Halloween, telling Dr. Loomis that Michael could not have gotten far because he cannot drive a car. Dr. Loomis replies that someone must have taught him. This is ironic, as in the 4-6 timeline he is likely the one who taught him how to drive. (This has no meaning in the H20 timeline, in which Wynn and the Curse of Thorn are not involved with Michael)

In the 4-6 timeline, Dr. Wynn is the leader of the Thorn cult, and the one who cursed Michael, making him the evil mass murderer he is.

He appeared in Halloween 5: The Revenge of Michael Myers as the Man in Black, killing at least six cops and breaking Michael out of prison, though his true identity is never revealed until Halloween: The Curse of Michael Myers. Wynn's intent was to have Jamie Lloyd's baby, Stephen, as the final sacrifice for Michael and then pass the Curse of Thorn to Danny Strode. However, before he got the chance, Wynn was presumably killed (offscreen) by Michael with a machete, along with the other cult members (onscreen).

The reason for Wynn's death being offscreen was in case they needed to retcon his death for his return in a sequel, however no sequels have been made to Halloween: The Curse of Michael Myers, with Halloween H20: Twenty Years Later being, like Halloween 4: The Return of Michael Myers, a direct sequel to Halloween II. Some fans speculate that he may have survived, as his death was never shown onscreen.

Portrayed by Robert Phalen in Halloween, Don Shanks in Halloween 5 (also the actor who portrayed Michael in this film), and Mitchell Ryan in The Curse of Michael Myers.