It's fair to say that back when I started watching Lost - a show about people who crash-landed on a strange island that, at the time, was rumoured to have dinosaurs on it - I probably wouldn't have believed the kind of places the story would go. With one season left to go, Lost appears to be leaving the sci-fi behind and heading out in the direction of supernatural theology. That didn't work out so well for Battlestar Galactica - could Lost carry it off better?

But let's not get ahead of ourselves. There's still this week's double-sized finale to cover. After last season's more muted 'jigsaw falling into place' ender, Season 5 goes back to the brain-warping, eyeball-popping tactics of previous cliffhangers. I'd like to say that started with the first scene, but let's face it - after this many seasons of Lost, you'd have to be pretty slow on the uptake not to have predicted immediately who the man on the beach was - although in true Lost fashion, no sooner is one mystery answered than its place is taken by two more. We know who Jacob is now, but who is his rival? What were they doing with the crew of the Black Rock? And what does that mean for our own island-dwelling cast?

If that reveal was immediately obvious then the series' next 'What's in the box?' mystery was only possible to speculate about. Frank's contrived reaction aside, the show did a good job of keeping us wondering what the case contained until the final moment, but few will have guessed that the answer was, well, the same as last year. Dead is dead, then.

On the lighter side of things, Rose and Bernard's return was particularly welcome, and provided a nice counterpoint to the melodrama of the main cast, who seem to travel directly from crisis to crisis without taking a breath. "We're retired," Rose informs the cast, with more than a hint of metatextuality about it. It's entirely possible that Rose and Bernard won't be seen again - though if they are, it's a fairly safe bet that they'll be wandering off into a cave to die, solving one of the show's oldest mysteries.

One other scene harking back to the show's early days involved Sawyer and Jack duking it out-school. Since I've never been a fan of Jack, it was enjoyable to see him get a pummelling from the character most frequently wronged by him. They should put that scene in every episode.

Despite her last minute save, it's Juliet who got the worst treatment this episode (and, arguably, season) as her transformation from a forceful, calculating Other into a fawning, weeping housewife became more or less complete. I guess the feminist movement hadn't reached The Island by the 70s. Her characterisation was inconsistent, her decisions all over the place and ultimately, her reason for wanting to detonate the bomb bordered on pathetic. It's a good job she's probably dead, because the character can't take any more mangling.

It's worth noting that even though the Losties' plan appears to have succeeded, there's no evidence so far that the future has actually been changed by the actions of the time-travelling cast members. Indeed, in some cases they've actually created the situation as we know it. Miles did raise the possibility that they might cause the very thing they were trying to prevent, and shortly after Chang loses his arm, apparently as a result of interacting with the Losties. It seems likely that Daniel was wrong, and that his plan to reset the future won't be quite as successful as he would have hoped. Although I have said in the past that I thought it was possible that the timeline would be reset at the end of this season, it now seems more likely that the characters still stuck in the 70s will simply be blasted back into the present, timeline intact. The fade to white (and as an aside, you know a show's good when it can confound your expectations by changing its LOGO) does suggest a time jump, after all.

Lost has still yet to deliver the perfect season finale to its viewers (they've now only got one more go to get it right - no pressure) and this one wasn't without its flaws. As well as being more than a little padded, with a relentlessly slow opening hour, there were also a few moments where the writing felt a little last-minute. Ben's insistence that he knew he was only ever talking to an empty chair smacks of being a last-minute retcon, while Jacob's insertion into past events of key characters added very little of substance to the plot. Although we're left with the impression that he puts people on their path to (or in some cases, back to) the island, it still feels like a desperately superficial attempt at working him into the canon.

As ever, we're left with a lot to think about following the conclusion of the series, and with a mere 17 episodes left - that's less than 12 hours' worth of material - Season 6 promises to be one of the most amazing seasons of TV ever - or one of the most disappointing. Either way - same time next year?

Check out a review of episode 15 here.