Plot summary
Desmond saves Claire from drowning and Charlie presses him to admit his precognitive abilities. He attacks Charlie when accused of cowardice, remembering what happened to him after the Swan blew. He wakes in 1996 and recognizes Charlie, but finds his abilities failing him after a fight he witnessed does not happen. While Desmond ring shops for Penny Widmore, shopkeeper Eloise Hawking correctly predicts that a nearby man will die, explaining that it was destined and that he would have died later even if saved. Desmond leaves Penny because he does not have enough money to support them and later witnesses the fight, realizing he miscounted the day it took place. He is injured trying to stop it and wakes up after the Swan explosion. In the present, Desmond admits that Charlie would have died both times he saved Claire, meaning he is destined to die soon.
Credits
Adapted from Wikipedia contributors, Lost season 3. HTML formatting and reference markers removed.