In part one of the three-part season finale, we see flashbacks of conflict between Walt and Michael when they were in a hotel, before getting on the Oceanic flight.
Walt wakes up and sees Danielle coming into the camp. He wakes everyone up. Danielle warns them that the “others” are coming. She tells the story of her team of six that were marooned on the island. Then she talks of seeing a pillar of black smoke six kilometers inland, and then the “others” came and took her baby, Alex. She says they have three choices: run, hide, or die. Later, while they try to get the raft to the water, they see the black smoke in the distance. Thinking to use the hatch as a place to hide, they ask Danielle if there are more explosives, and she says yes, at the Black Rock, in the dark territory. Doc Arzt goes along out of concern about the dynamite’s volatility. Kate goes along to help and because she hates goodbyes. Danielle mentions her team getting infected in the dark territory, and Montagne losing his arm. She also says that the “monster” is a security system to protect the island.
In a flashback, we see Ana-Lucia at the bar with Jack, making conversation, asking prying questions, and drinking because she is in the tail section near where the wheels come down. She has to talk, but tells him “the worst part’s over,” presumably referring to his father dying.
James Ford (aka Sawyer) has a flashback about being in a police station in Sydney. He is being deported, and is told he will never set foot in Australia again. On the island, Sawyer seizes the opportunity to tell Jack about meeting Jack’s father, and what he told him. He says, “Small world, huh?”
Sun gives Jin a list of phoenetic wirds to help him communicate on the boat. He says he is sorry and that he is in this place because he is being punished for what he put her through. They make up, and he says now he will save her.
The boat launches.
This is the first episode with multiple flashbacks by multiple people, unless I am mistaken.
The notion that the smoke monster (which, as of this point, we still haven’t seen) is a “security system” would be mentioned or hinted at time and again. It isn’t hard to retcon this from the perspective of things that were said later – this might be a deception started by “smokey” himself, for all we know. And when we later learn where Danielle “learned” this from, we have no reason to think that the information was accurate.