Matthew Fox in Lost by Art Streiber/ABC Matthew Fox in Lost by Art Streiber/ABC
For lots more on Lost

, read our fresh Q&A with Naveen Andrews and our character profile of Jack, check out Hein Sight's look at the hype, see what the Roush Dispatch has to say, and flip through our Lost

photo galleries. The when: Thursdays at 9 pm/ET, with the Season 4 premiere airing Jan. 31. (A "recap" special precedes it at 8 pm.) Why Watch?: We suspect that for many the question isn't "Why watch Lost?" but "Why should I watch Lost again?" When Lost premiered back in 2004 it was an instant sensation that had just about everyone buzzing about what would happen next. But those who wanted a steady stream of answers were soon frustrated, as its unresolved mysteries were multiplying at a dizzying rate. If the first season was a pop-culture phenomenon, and the sophomore cycle - with its soggy midsection and general lack of forward momentum - was a mild disappointment, then Season 3 was proof that Lost is the real deal, a bizarre, complex television masterpiece that combines insightful character work with an ever-present sense of dread over what the future holds. It's clear now that the show's creators are playing fair, and that all of the clues and mysteries will fit together in the end like pieces in a gigantic jigsaw puzzle. If you were ever a fan of Lost in the past, it's time to rent the Season 3 DVDs and get ready for more shocking surprises when the show returns. And if you've never seen Lost and are afraid of being too confused to start now, don't worry. That just means you're part of the club. Who's who: The sizable cast can be divided into three groups of people: the Oceanic Flight 815 survivors (whom we've been following since the first episode); the Others, a tribe of natives (and the occasional recruit from the outside world) who have been living on the island for some time; and a new side in this conflict, the mysterious rescue party who have found the island and, if the Others' leader Benjamin (Michael Emerson) can be believed, are the show's true villains and represent "the beginning of the end." What's next: The third season finale of Lost delivered the mother of all plot twists: The flashback revealed itself to be a flash- forward in which some of the survivors, including at least Jack (Matthew Fox) and Kate (Evangeline Lilly), managed to escape to the real world. But it wasn't exactly a happy ending. Jack, now sporting a homeless-man beard, had spiraled into suicidal depression and was ranting that he desperately needed to "go baaaack" to the island. The entire structure and focus of the show has been dynamited, and the new questions that have been raised ("What happened to the rest of the crash survivors?") are making us just as hungry for new episodes as we were back in the first season. Say what?!: The writers originally wanted to kill off Jack at the end of the first episode in order to show that nobody was truly safe on Lost. But even more surprising? An early choice for Fox's role was Michael Keaton! What do you say? A show like Lost practically demands its fans to ask each other what they think is really going on and what will happen next. Who made it off the island? Or for that matter, why would anyone choose to stay? Who is the mysterious Jacob? Will Kate ever choose between Jack and Sawyer? And the biggest mystery of all: Why is the rescue party so anxious to get their hands on the island, what exactly are its special properties, and why are Benjamin and now Locke (Terry O'Quinn) so willing to kill in order to protect it? - Jack Rodgers Use our Online Video Guide to catch up on past episodes of Lost, as well as a sneak peek the Season 4 premiere. More Strike Survival guidance: " Should You Seek Treatment from Gabriel Byrne? " CSI Exclusive: The Secrets Behind This Week's Repeat " Movies-on-TV: Ken Fox's Picks for the Week of Jan. 28