We flash back/forward (who knows at this point) to the last scenes of season 3, when Jack and Kate meet at the L.A. airport.
Jack, who's on the verge of a mental breakdown, insists they need to go back to the island. He mentions Jeremy Bentham, the unseen man in the coffin, who told them they needed to return. Kate gets angry. There's no way she's going back.
Back in island time: The Others, along with Kate and Sayid, ambush the mercenaries as they bring Ben to the helicopter. Ben escapes and Keamy is evidently killed by Richard Alpert.
Meanwhile, Jack and Sawyer encounter Hurley and Locke at the Orchid Station. Locke tells Jack he should stay on the island, but if he leaves he mustn't reveal anything that happened. The island must be kept secret.
Ben then shows up and he and Locke descend in an elevator deep beneath the station in order to "move" the island.
Jack, Sawyer and Hurley go back to the helicopter where they meet up with Sayid, Kate and Frank, the pilot, who loads them up and flies off toward the freighter.
Back on the beach, Daniel continues ferrying people to the freighter. He stresses to Miles and Charlotte that they need to get off the island quickly. He seems to realize what Ben and Locke are up to and what the Orchid Station is all about. Miles says he's staying and, privately, he hints to Charlotte that he knows she has a history with the island. It's her home. Daniel doesn't hear this, but later Charlotte tells him she also will stay behind.
Back in the air, the helicopter is losing fuel. The gas tank was pierced during the gun battle between the mercenaries and the Others. Those on board throw stuff out so they can make it the freighter, but the load is still too heavy. Sawyer whispers something to Kate--something he wants her to do is she's rescued (most likely involving his daughter Clementine and Clementine's mother Cassie). Then he jumps out in the ocean. Later we see him turn up on the beach--he's ok.
Beneath the Orchid Station, Ben puts on an orientation video for a confused Locke as he tosses metal chairs and other objects into a mysterious chamber. The video seems to explain Dharma experiments with time and space and cautions against putting anything metal in the chamber. Locke becomes concerned, but then the video messes up and the elevator from up above arrives with someone else in it. It's Keamy, whose body armor apparently saved him from Alpert's bullets.
Keamy tells Ben there's a monitor on his arm. It's connected to the explosives on the boat. If Keamy's heart stops, the bomb goes off. Enraged over Keamy's taunts about killing Alex, Ben flips out and stabs Keamy in the throat. Ben tries to keep Keamy alive, but it doesn't work. The monitor switches on the explosives.
On the freighter, Desmond, Michael and Jin struggle to find a way to disable the explosives, nothing seems to be working. Shortly before things are set to blow, the helicopter arrives. In a few chaotic moments, Desmond and Sun, with baby Aaron, are loaded onto the chopper but Jin doesn't make it on board before the helicopter departs.
Back in the room with the explosives, Christian Shepherd appears before Michael and tells him "you can go now." And the boat blows up.
Ben then tells Locke to go back up the elevator to join the Others. Ben will do the work of moving the island. He says that anyone who moves the island must leave it and can never return. Locke is the leader of the Others now.
Locke departs and Ben, wearing a parka because he's going "someplace cold," goes through the weird chamber into a tunnel and down a ladder into a frozen cavern with an ancient-looking wheel in it. He struggles to turn the wheel and everything outside goes strange--weird sounds and light, the island is moving.
At the same time, those in the helicopter are heading toward the island. There's no place else for them to go. But as they approach, the island vanishes and the chopper loses control. The passengers inflate a life raft and put on life jackets. The chopper plunges violently beneath the waves, but everyone manages to get on board the raft.
Meanwhile, Daniel and his raft-load of people are out on the water. We don't know if they disappear along with the island or not.
Later, the helicopter passengers encounter a boat. It's Penny and her people and they are taken aboard. A story is concocted to cover up what really happened after the Oceanic crash and Jack, Kate, Aaron, Sayid, Hurley and Sun are put on board a primitive raft to make it look like they are the only survivors. This explains why there is an "Oceanic 6" and how they came to be rescued. Desmond's re-arrival to the outside world is evidently kept secret.
Back in civilization, in various scenes, we learn that Jeremy Bentham has visited Walt, Jack, Kate, Sayid and Hurley, but we still don't know who he is. However, it's evident that events are conspiring to reunite the crash survivors.
Sayid is shown killing a man stationed in a car outside the mental health facility housing Hurley. He goes inside and persuades Hurley to come with him to a "safe" place. Meanwhile, a drunken, messed-up Jack goes back to the funeral home late at night. He breaks in and walks up to the mystery coffin. A voice behind him says "Hello Jack." It's Ben, who knows that Bentham has visited the Oceanic 6 and was trying to persuade them to return to the island.
Jack says Bentham told him "bad things" had happened on the island after their departure. Ben insists they all need to go back, including Bentham, who is dead. At that moment, we finally see who is in the coffin. It's Locke!
* The man in the Orientation video identifies himself as Halliwax, but it's the same guy (or appears to be the same guy) who has identified himself as Dr. Marvin Candle and Dr. Mark Wickmund in other orientation videos/films.
* The parka Ben is wearing says "Halliwax" on it and it's the same garb he's shown wearing when he arrives, teleported or however, in the middle of the Tunisian desert.
* There's a 10-month time lag between the time Ben spins the wheel and when he turns up in the desert--so obviously there's something wacky going on in terms of space and time in relation to the island and its "relocation."
* During the episode, ABC aired an ad from "Octagon Recruiting," which plugged a recruitment drive July 24-27 in San Diego. Those interested were directed to this site, where you can register your interest by providing your e-mail address. Here's a screen shot of what you'll see:
July 24-27, incidentally, are the dates for Comic-Con 2008, the huge pop culture gathering that takes place in San Diego every summer. So, evidently, the "Lost" folks have plans for something big down there then.
* Did Daniel and the people in his raft vanish with the island? If not, where are they?
* Did Jin survive the freighter explosion? How about Michael?
* Claire's ghost (I guess), tells Kate not to bring Aaron back to the island. Why not?
* Played backwards, the voice Kate hears on the phone during her dream says "The Island needs you, you need to go back before its to late."
* What "bad things" happened on the island? How can the Oceanic 6 help by going back?
* How will they get back to the island?
* Is Jack needed on the island to resolve matters between himself and his seemingly dead dad?
* Why did Locke adopt the identity of Jeremy Bentham and how did he manage to visit the Oceanic 6? Bentham, obviously, contains the word "Ben" in it. Was Locke making a reference to Ben when he chose this name?
* Jeremy Bentham is the name of a philosopher. According to Wikipedia:
He was a political radical, and a leading theorist in Anglo-American philosophy of law. He is best known for his advocacy of utilitarianism, for the concept of animal rights, and his opposition to the idea of natural rights, with his oft-quoted statement that the idea of such rights is "nonsense upon stilts." He also influenced the development of welfarism.
As requested in his will, [Bentham's] body was preserved and stored in a wooden cabinet, termed his "Auto-icon". Originally kept by his disciple Dr. Southwood Smith, it was acquired by University College London in 1850. The Auto-icon is kept on public display at the end of the South Cloisters in the main building of the College. For the 100th and 150th anniversaries of the college, the Auto-icon was brought to the meeting of the College Council, where he was listed as "present but not voting". Tradition holds that if the council's vote on any motion is tied, the auto-icon always breaks the tie by voting in favour of the motion.
The Auto-icon has always had a wax head, as Bentham's head was badly damaged in the preservation process. The real head was displayed in the same case for many years, but became the target of repeated student pranks including being stolen on more than one occasion. It is now locked away securely.
* How did Locke/Bentham die? Will he spring back to life if returned to the island?
* Did Alpert purposely not kill Keaney?
* Is this man, shown among the Others, the psychic who helped persuade Claire to take Flight 815?
* The wheel and the ice chamber containing it seem ancient, much like the huge statue Sayid, Jin and Sun saw at the end of season 2. It seems like the island and its mysterious properties have a long, long history.
* What is Charlotte's history? Is she an Other offspring? Were her parents involved in the Dharma Initiative?
* In London, Sun is shown confronting Widmore. Will she work with him to locate the island? Will this put her at odds with Ben, Jack and the rest?
* Two alternate endings for this episode were filmed. You can see them here.
Lost Season 4 Episode Guide
The Best Lost Sites on the Web
Lost: What we STILL don't know