When a boy who can make people lose their memories robs the Talon, Clark goes after him but gets total amnesia. Chloe finds out what happened and has to tutor Clark in the use of his superpowers and make sure he doesn't accidentally reveal his secret. While Clark, Chloe, and Lois try to track down Kevin, Clark takes advantage of his "new life" to ask Lana on a date. And Lex tries to turn Clark's memory loss to his advantage by getting him to reveal the secret of the caves.

Eric finds out that in order to graduate he has to pass PE. The PE teacher turns out to be Kelso's older brother and Donna's xboyfriend, Casey.

Last night, American Idol's Top 6 sang their hearts out in hopes of winning America over. Find out tonight who will survive and who will be sent home. The contestant who received the fewest votes will be eliminated from the race for the title.

Sophia, Nadia's old caretaker, contacts Nadia, after being severly beaten. Sophia tells Sloane that she was beaten up because someone was after Nadia, so him and Jack decide to tell their daughters the truth, that Elena Derevko has been watching both of them for a decade. Also, JAck's doctor advises him to tell Sydney about his sickness.

The girls go to South Africa and learn about the country's fashion and history.

When a college student is beaten, shot to death and his apartment ransacked in what appears to be a drug-related hit, the team must track down his killers. After examining the evidence in the murdered student's apartment, the team finds traces of pure, unprocessed heroin and discovers that the victim had a female roommate who is now missing. Meanwhile, Stella's aggressive interrogation tactics with a witness threaten her police badge.

The swamplands of Georgia's Altamaha River Basin are all that one would expect of a Primordial bog: dank, menacing, swimming with slithering creepy-crawlies and, of course, alligator-infested. This is the welcoming environment Les Stroud will be immersed in for seven sweaty days and bone-chilling nights.

TONIGHT: Author of "One Nation Under Therapy," Christina Hoff Somers! Plus, "International Pamphlet."