In which episode did Charlie Pace die?

Charlie Pace died in “Through the Looking Glass,” the two-part third-season finale of *Lost*.

Charlie infiltrates the Looking Glass station with Desmond’s help to disable the Others’ signal jammer. After obtaining the code, he shuts down the equipment and receives a video call from Penny Widmore. Penny reveals that she did not send Naomi’s boat, confirming Charlie’s warning that it is “not Penny’s boat.”

Mikhail Bakunin then detonates a grenade outside the station, shattering the communications-room window and flooding the chamber. Charlie locks the door from inside to save Desmond, knowingly sacrificing himself. Before drowning, he writes the warning on his hand so Desmond can see it through the glass.

The episode is sometimes described as episodes 22 and 23 of season 3 because the original broadcast was an 85-minute two-parter. That format can cause confusion with “Greatest Hits,” the preceding episode, but Charlie’s death occurs only in the finale.