It’s performance night for the final four — Kree, Candice, Amber, Angie — on “American Idol” (Fox at 8 p.m.), as the road for the first female winner on the show in six seasons continues.

At first glance, Charlie is just a nerdy hacker — but while training her how to be a hunter, Dean suspects she’s actually keeping a dangerous secret on “Supernatural” (CW at 9).

The detectives run into a problem with a rape investigation on “Law & Order: SVU” (NBC at 9) when a student pledging a sorority says she was attacked, but the university refuses to cooperate.

Installment No. 3 of “Nova: Australia’s First 4 Billion Years: Monsters” (WETA, MPT at 9) looks at giant creatures in the Mesozoic Era, including one that ate enormous cephalopods — the size of truck tires — as snacks.

Polly realizes that her daughter might not be coping well with her divorce on “How to Live With Your Parents (For the Rest of Your Life)” (ABC at 9:30), while Polly’s own parents take off to visit a sick relative.

FINALE WATCH: Stylist Brad tries to please his client/George Clooney’s girlfriend Stacy Keibler on the second-season finale of “It’s a Brad, Brad World” (Bravo at 10), but the episode was filmed last fall when Hurricane Sandy hit, and he doesn’t have access to important New York showrooms.

Elizabeth and Philip realize that they may have walked into a setup on this season’s penultimate episode of “The Americans” (FX at 10), as Stan uncovers some surprising information.

Juliet starts spending a lot of time with someone who Shawn thinks is a dangerous killer on “Psych” (USA at 10), but unfortunately for Juliet, Shawn is distracted as he decides to bond with Woody.

A former candidate for the paramedic job comes back with some serious accusations against Severide on “Chicago Fire” (NBC at 10).

Things take a turn for the worse at a New Jersey steakhouse on “Restaurant Stakeout” (Food Network at 10) when the crew suspects there’s a thief working in the kitchen.

“Late Show With David Letterman” (CBS at 11:35) hosts actress Kate Hudson, magician Ricky Jay and singer Selena Gomez.

Actress Emily Blunt is on “The Tonight Show With Jay Leno” (NBC at 11:35), along with a performance by Black Rebel Motorcycle Club.

“Jimmy Kimmel Live” (ABC at 11:35) has actor Topher Grace, “Mythbusters” team Adam Savage and Jamie Hyneman, and musical guest Depeche Mode.

— Emily Yahr