Lost is almost inexplicably better than it sounds – a bunch of people stranded on a tropical island after a plane crash, brought together by FATE, each with SECRETS, which we find out about through FLASHBACKS. I should have known it wouldn’t be long before amnesia featured in the plot. JJ Abrams’ last series Alias was good, but it’s not any more and it was never this good. This is genuinely brilliant television, the kind you could just string together to make a great film.

If Alias was defined by its ridiculous cliff-hangers, Lost is defined by ridiculous mysteries. Since the start of the series twenty-five episodes ago, the following elements have cropped up and been developed to the extent detailed here:

• The Monster: We don’t know anything about the monster. It might be big. It might not exist. It could also be robotic or organic, or ethereal, or none of these.
• Jack’s Dad: Jack’s Dad appeared. We don’t know why or what was going on.
• The Hatch: Locke discovered a hatch. We don’t know what it’s doing there or what’s inside, or what the thing is it’s built into. Since the hatch was discovered, virtually every episode has been about it. So far, we have discovered: nothing. Once the hatch lit up. We don’t know why.
• The Numbers: Hurley won the lottery with some numbers. They might be cursed, or not cursed, or it might be fate. Or magic.
• The Others: There might be others on the island, or there might not, or they might not be on the island, or they might not be others. If they are and they are we don’t know who they are or what they’re doing there or what they want.
• The Kid: The kid knows something about the hatch. We don’t know how or what and now he’s gone forever.
• The French Woman: There is a French woman on the island. Something killed the crew she was with. We don’t know what and now she’s gone mad.
• The Polar Bear: A polar bear appeared. We don’t know why or where it came from or how it got there. It was killed and never mentioned again.
• The Other Half Of The Plane: We don’t know where it is or what happened to the people on it. They might be still alive, or dead, or trapped sixteen years in the past with a magic time-traveling radio.
• The Island: The island might have a will of its own, though it might not and if it does we don’t know what it is, why it has it, or how it works.

Whichever of these wildly vague concepts you might be hoping for clarification on, you’re perpetually disappointed. The appeal is that by failing to resolve any of these plot lines, they’re never cheapened by specifics. Their enigma gives them a lasting menace that only improves the tapestry of sinister threats mounting around the ever-diminishing survivors. All of them verge on the mystical without being scientifically inexplicable – given a degree of imaginative license. We still don’t even know what genre we’re working in – sci-fi, fantasy, supernatural or real-world.

But the writers seem content to leave that ambiguous too – they’ve got plenty of stories to tell in flashbacks to the castaways’ previous lives, and some of those have been extraordinary. The glimpses of the mysteries, too, have been expertly judged. The one ‘Other’ we’ve seen – despite being just some guy – is one of the most unsettling bad guys ever. Even small things like making sure you realise dynamite is dangerous – they have the dynamite expert annihilated by it when handling it as carefully as he can, and from then on you’re screaming at the characters to walk slower, don’t put the dynamite in their packs, don’t use flaming brands for torches.

Locke: Hugo, take these extra sticks back a couple hundred yards.
Hurley: Me? Oh, okay. Got it. ... Can I have a flashlight? 'Cause, er, the torch-near-the-dynamite thing's not making a whole lot of sense to me.

Which leads nicely into the other reason it’s great: Hurley. On paper he sounds awful – a fat comic relief character who just says “Dude,” “Yo,” or “That was messed up” at oppourtune times. But that fails to take into account the sheer brilliance in the timing of his Dudes, Yos and That-was-messed-ups, and also that he says them flatly, rather than in the Keanu Reaves surf-slang drawl. Essentially he’s just a guy who watches a lot of TV, in a TV series, saying the things you feel like saying yourself (as above).

The comments below assume you are up to date with the story as it’s being aired in the US – they may spoil things for you if you’re not.