Let's begin at the beginning of the Lost Season 5 finale ... Two men are talking on the shore of our island - Jacob and a man played by Titus Welliver. The man says he wants to kill Jacob, and says he'll one day find a "loophole" to allow him to do this ... This happened a long time ago...

Back in our time - that is, the past few decades - Jacob visits most of our original, now still surviving, Flight 815 passengers. Some, like Saywer and Kate, are visited when they are children. Others, like Jack and Locke, when they at low or desperate points in their adult lives. Jacob visits Sayid, distracts him, so he can't stop Nadia from being hit and killed by a car. Hurley's visit is the most recent - its purpose to convince Hurley to get back the island.

Tonight's episode, then, among the many intriguing, fabulous things it is, is the story of Jacob. It provides at least part of an answer to something I've been saying since the beginning of the second season - that the key to understanding Lost resides, somehow, in the inexplicable coincidences in the flashbacks, in people who presumably first met on Flight 815, or on the island, crossing paths in the past - such as Desmond and Jack running into each other on the steps of the stadium, Kate's mother serving Sawyer in a diner, etc. We didn't see Jacob in those intersections tonight, but we saw him in enough places and times to make it plausible that he could have manipulated those coincidences to happen, too...

But Jacob's story is also as short as it is long. And it ends with one of the best surprises in the series: Locke did not come back to life when Flight 316 crashed on the island this season. No, not at all. The Locke who has been walking around on the island is the man who was talking to Jacob on the shore all those centuries or whenever ago. He has somehow taken Locke's form - and inexplicably has at least some of Locke's memories - and in that form goads Ben into killing Jacob. That, apparently was the loophole - the man could not kill Jacob himself, but he could drive someone else to do that...

Which may explain a lot of things. Let's say no ever came back to life on the island? Coming back to life certainly seems like news to Richard - his people can cure the critically wounded, not the dead. That's why young Ben but not Faraday was saved. Did this shape-shifter look like Christian, to manipulate Jack; look like Alex to manipulate Ben; and who knows who else?

Dead is dead, that seems clear now. And it brings us to the other great part of tonight's story.

Jack brings the core of the hydrogen bomb to the Swan site. There are some wonderful scenes with Jack and Sawyer - who, as he's been throughout much of this season, is a more admirable character than Jack. The plan is that the bomb will wipe out the island, 815 won't crash, and nothing we've been seeing for the past five seasons will happen. Sayid is badly wounded, so this might be good for him (though Richard could well cure him) ... but for everyone else?

As I wrote last week, and in previous weeks, the plan can't succeed. Faraday was right when he said the past can't be changed (and he was too torn by grief to be thinking clearly when he said it might be changed, after all). Miles seems to best get this now - he says maybe the bomb going off will cause the "incident" to happen - will cause the reality we have seen to occur.

Jack drops the bomb into the shaft, as the digging already going on unleashes a magnetic force that starts pulling the equipment apart. Phil from Dharma gets killed - good riddance (but good acting by Patrick Fischler). Juliet gets pulled into the shaft. She's hanging on. Sawyer and Kate try to save her (great line from Sawyer - "where you going, Blondie?") But the force is too strong. Juliet leaves go because doesn't want to pull Sawyer in and she falls down the shaft.

But she's not killed. And at the bottom of shaft, she finds the core of the h-bomb, still intact. She pounds on it. And - it goes off.

Have the past five years been destroyed? Will they never happen?

Of course not. Of course they will. I'm sure Miles was right. And we'll see how this all plays out - with the new "Locke" next year... The fact is that we can't be sure what the blast will do, other than that it won't change the past and wipe out five years. Conceivably, it could throw our people from 1977 back into the present ... it could even, perhaps, save Juliet in this way.

Minor quibbles ... I found Jacob coming in and out so fast a little unsatisfying, and we could have used a little more precedent in the story for the shape shifting. But, all in all, a splendid resolution to this season and a powerful set-up for the next, and final, season.

And, oh yeah, Rose and Bernard! Someone asked me, in a comment somewhere about one of my Lost reviews this season, if I thought we'd ever see those two again. I said I was sure they'd turn up in the final episode of the season, as they usually do. And, sure, enough, they did (taking care of Vincent!) - both looking better and happier than ever!

More Lost - see : The Richard-Locke Compass Time Travel Loop ...

and Lost Returns in 5 Dimensions and 5.3: The Loops, The Bomb ... 5.4: A Saving Skip Back in Time ... 5.5 Two Time Loops and Mind Benders ... 5.6 A Lot of Questions ... 5.7 Bentham and Ben ... 5.8 True Love Ways ... 5.9 Two Times and a Baby ... 5.10 The Impossible Cannot Happen ... 5.11 Clockwork Perfect Time Travel ... 5.12: Ben v. Charles, and Locke' Slave ... 5.13: Lost Meets Star Wars and the Sixth Sense ... The Problem with Baby Aaron and the Return of the Oceanic Six ... 5.14: Eloise, Daniel, and Obsession Trumping Paradox ... 5.15: Moral Compasses in Motion