We'll start this rundown of the episode "Sundown" with a look at Sayid's sideways life in 2004:
After a trip to Sydney for business (translating contracts for an oil company), Sayid visits Nadia... and her husband, Sayid's brother. They have two kids. It's clear that Sayid is fond of the family, and especially of Nadia, as he carries around a photo of her. Late one night, Sayid's brother tells his brother that he is in major trouble with a loan shark and wants Sayid to take action. Why?
Because he knows what Sayid did for the Iraq army and he knows "what kind of man" Sayid is. Sayid says he cannot help because he's no longer that man. But Sayid's brother is soon beaten, clearly by the loan shark. Sayid initially does nothing because Nadia pleads with him to be there for the kids. She later asks him why he never pursued her and he says because he does not deserve her, following what he did in the army.
The loan shark and his men soon capture Sayid, however, and this sets him off. He uses his military training to take them all out, even when the main guy - Keamy! - tells him the debt is forgiven and they can forget everything. Sayid's response: I can't. He then shoot Keamy and hears a rumbling in the giant freezer (he was taken to a restaurant kitchen). A man is tied up inside there. It's Jin.
BACK ON THE ISLAND: Dogen tells Sayid he must leave the Temple, but quickly changes his mind when Claire walks in and says "he" wants to talk. Dogen then gives Sayid a mission: if you're really a good man, take this knife and stab the person waiting outside. He'll appear to you as an acquaintance that has died, but kill him before he can speak.
Sayid steps outside and runs into Fake Locke. He plunges the knife into his chest, but it does nothing. Fake Locke explains that Dogen knew it would do nothing and, once again, was trying to set up Sayid to be killed by someone else. Fake Locke tells Sayid to take a message to those in the Temple. It's this:
Jacob is dead. Everyone in the Temple will die if they don't take Fake Locke's side and leave the island. Everyone panics and leaves, but Sayid first goes back inside to return the knife to Dogen. He learns of Dogen's story: after drunkenly celebrating a promotion, he got into a car accident that critically injured his 12-year old son. Jacob visited him in the hospital and said he could save Dogen's son's ife, as long as Dogen agreed to go to the island and never see his son again.
Soon after hearing this, Sayid grabs Dogen and drowns him in the magical Temple pool. He then slits the throat of Lennon.
At this point, Ben, Ilana and Lapidus are on the scene. They take Miles and find a secret passageway through the Temple walls. It's just in time, too, because Fake Locke has entered now that Dogen is dead. He kills all remaining in his path. Kate - who returned earlier and was told Claire was being kept in Temple's hole - jumps down and joins Claire, where the latter says they'll be safe. This is how we end the episode:
An infected, darkened, proud Sayid and Claire walk out of the Temple and into Fake Locke. He's surrounded by his new team, those that escaped the Temple before. Kate also stumbles out, confused about what's going on. Fake Locke turns and leads his side into the jungle. Cut to black.