Sayid's life is placed in grave danger after he stumbles upon the source of the mysterious French transmission, the woman Danielle Rousseau (guest-star Mira Furlan). She was on the distress call and is found alive. Meanwhile, Hurley has a ridiculous plan to make life on the island a little more civilized. The plan involves golf clubs he finds in the debris, and it looks like it just might work. Lastly, we flash back to Sayid's childhood friend Nadia as well as his participation in hostage situations in Iraq.

When Hurley becomes obsessed with the French woman and heads into the jungle to find her, Jack, Sayid and Charlie have no choice but to follow. Hurley flashes back to the hugely life-altering experience he had before boarding the plane.

The French woman-Danielle Rousseau-shocks the survivors by showing up to the camp with a dire warning about "the Others" who are on the island, and the black smoke that precedes them. Meanwhile, Michael and Jin ready the raft for sailing. In flashbacks, we see the survivors final moments before they boarded their fateful flight.

The castaways on the raft are surprised at sea by something unexpected. Meanwhile, remaining islanders attempt to blow open the hatch, and a visitor to the encampment might be a threat to Claire's infant son.

After Sun is attacked, some of the survivors begin to think that one of the "other survivors" might be one of "The Others." When French woman Danielle Rousseau leads Sayid to a mysterious captive in the jungle, he becomes determined to find out if he is one of "The Others". Meanwhile, Sawyer discovers Hurley’s potentially devastating breach of the survivors’ trust and blackmails him into helping track an elusive island creature that won’t leave Sawyer alone.

A mysterious illness that baby Aaron suddenly contracts sends a desperate Claire, Kate and French woman Danielle to return to the same area where Claire was initially kidnapped. It is there where she believes she can find a cure for Aaron's illness. In the meantime, Jack and Locke are doing their best to keep their prisoner a secret from the rest of the survivors on the island.

Kate is still struggling over their decision to leave Jack in the hands of the Others as she and Sawyer return to their camp. Meanwhile, Hurley finds an old van in the jungle and attempts to use it to help a fellow survivor in need of faith and hope. Flashbacks reveal more of Hurley's tumultuous past with the numbers curse.

On their mission to rescue Jack, Kate, Sayid, and Locke stumble upon a mysterious structure surrounded by farm animals and meet its strange inhabitant. Back at the camp, in order to reclaim his belongings, Sawyer plays in a ping-pong competition.

Claire has an idea to send a message to the outside world. Charlie, however, is resistant to the idea, and Desmond tries to sabotage the plan. As Claire tries to get the truth behind their actions out of the pair, she remembers traumatic events from her past. Meanwhile, the rescue party encounters a dangerous obstacle.

When Kate and Locke arrive at the Others' camp, Ben promises to tell Locke the island's secrets as long as he stops his destructive plan, and Kate's reunion with Jack doesn't go very well when she learns that the Others have offered him a deal. More of Locke's troubled past is revealed.

After abandoning the Others, Locke takes Sawyer on a trek through the jungle to help him eliminate a common enemy. Meanwhile, back at the beach, the parachutist Naomi has crucial information about flight 815.

While Jack devises a plan to do away with "The Others" once and for all, Sayid uncovers a flaw in "The Others'" system that could lead to everyone's rescue. But it requires Charlie to take on a dangerous task that may make Desmond's premonition come true.

A Charlie-centric episode.

The season 3 finale finds the castaways preparing for an invasion by the slightly less mysterious Others, while Charlie and Desmond find more than they were looking for in the underwater "Looking Glass Hatch".

The season 3 finale finds the castaways preparing for an invasion by the slightly less mysterious Others, while Charlie and Desmond find more than they were looking for in the underwater "Looking Glass Hatch".

They thought they had met the enemy. They thought they had seen evil. They thought wrong. As the new season begins, the survivors feel that rescue is close at hand, but they don't know whether or not to believe Charlie's final message that the people claiming to liberate them are not who they seem to be. As unlikely alliances are formed, those they thought could be trusted may turn against them, as the enemy of their enemy becomes their friend. But who can be trusted? Is rescue really as close as it seems?

The survivors begin to question the intentions of their supposed rescuers when four strangers arrive on the island.

Locke's hostage may be the key to getting off the island, so Sayid and Kate go in search of their fellow castaway in an attempt to negotiate a peaceful deal.

Sayid confronts Ben's spy on the freighter, and Ben urges daughter Alex to flee Locke's camp in order to survive an impending attack.

Ben finally takes his revenge on Widmore after accepting the Man in Black's request for assistance. Jacob explains the purpose of the candidates, and Jack volunteers to take his place. The search for Desmond reveals that he has been rescued and the Man in Black plans to use him to destroy the island. In the flash sideways, each person ends up on their way to a concert.