'When am I?" John Locke asks during tonight's fifth-season premiere of "Lost." And you'll know exactly how he feels, as the two-hour episode skips through time like a needle on a vinyl disc - during an earthquake. The "Lost" time-travel machine is set at full surge, as the narrative, the island itself, and the characters, both dead and alive, leapfrog crazily among the past, present, and future tenses.
Spoilers? Don't worry. The premiere, at 9 on Channel 5, is so riddled with clues, so crowded with incident, and such a jigsaw of time scheming, it's hard to imagine what major, as-yet unknown facts I could disclose here. There are 342 tiny reveals tonight, and yet no one plot wallop that's going to take the top of your head off. Still, please don't read any further if you're a purist and want to re-enter the temple of "Lost" unawares, to let the mystery fully work its chaotic logic on your imagination.