Watch Lost S06e11 Here

On the Island in 2007, Charles Widmore brings Desmond back as the "package" required for his mission. Widmore subjects Desmond to a severe electromagnetic event—a test he survives because of his unique resistance to such energy. This survival is crucial; it triggers a "flash" of consciousness that allows Desmond to perceive the "Flash-Sideways" reality. After the experiment, a zen-like Desmond agrees to help Widmore, though he is soon intercepted by Sayid.

: Tasked with retrieving a drug-addled Charlie Pace for a concert, Desmond experiences a near-death event when Charlie drives their car into the ocean.

: Awakened to the truth, Desmond meets Daniel Widmore (Faraday), who explains that their world is "not their correct path" and that a nuclear event may have altered reality. This encounter leads Desmond to find Penny at a stadium—echoing their first meeting in the original timeline—where a single handshake causes him to faint from the emotional and temporal impact. Lost Recap: Season 6, Episode 11, “Happily Ever After”