TONIGHT'S MUST-SEES

"LOST" SEASON FINALE, 8-10 P.M., ABC

Brilliant and befuddling, "Lost" keeps reminding us that the best things in life are rarely the easiest.
With just one 17-episode season remaining, this has become a perplexing web of time travel, one in which dead people return and life gets do-overs. Some viewers try to keep up with it all; an hour-long clip show at 7 p.m. will try to explain what has happened. That's not necessary, though; just settle back and enjoy a grand ride.
When last seen, Locke was leading people on a stroll to meet the unseen soul who has been giving orders. Locke claims he's going to kill him — if he even exists.
In another time frame, Jack and others have reached the hydrogen bomb; if he blows up the island, Jack feels, it all will be reversed. Meanwhile, Sawyer (alternately known as LeFleur) is leaving on a submarine with his two loves, Juliet and Kate.
Tonight, Jack's plan and Locke's plan meet resistance. Then, we assume, surprising things happen.

"AMERICAN IDOL," 8 P.M., FOX

There is no logic to a world in which two of the season's biggest events happen simultaneously.
Tonight, we learn who will facing off in next week's finale. The field includes two talented — and immensely likable — guys (Kris Allen and Danny Gokey) and one (Adam Lambert) who transcends that with amazing gifts. Tape this and watch "Lost," or vice versa.