What is the title of the episode where Desmond is first introduced?

The episode where Desmond is first introduced is “Man of Science, Man of Faith.” It opens season 2 of Lost and first aired on September 21, 2005, immediately after the season 1 finale revealed an underground hatch beneath the island.

The episode introduces Henry Ian Cusick as Desmond Hume. In flashback, Jack Shephard meets Desmond while running at a stadium, before either man realizes that their paths will cross again. In the present-day story, Jack, Locke, and Kate enter the hatch and discover that its occupant is the same man Jack recognizes from his past.

The title reflects one of the show’s central tensions. Locke often represents faith and destiny, while Jack is associated with science, medicine, and evidence. The episode complicates that contrast by showing Jack confronting events that challenge his rational understanding of the world.

“The Constant” is a later, celebrated Desmond-centered episode from season 4. “Live Together, Die Alone” is the season 2 finale that expands Desmond’s backstory, while “The Orientation” is another early hatch episode—not Desmond’s debut.