V, Dancing with the Stars, and NCIS: Los Angeles

NCIS's Abby appears on NCIS: Los Angeles tonight.

8 p.m., ABC

V

In the last episode of V before 2010, Erica (Elizabeth Mitchell) discovers a biological threat that could be connected to the Visitors.

Season 9 finale, 9 p.m., ABC

Dancing with the Stars

The three-hour season finale includes danceoffs, performances by Whitney Houston, and appearances by all this season's contestants. Oh, yeah, and the winner is chosen.

9 p.m., CBS

NCIS: Los Angeles

NCIS's Abby Sciuto (Pauley Perrette) visits the West Coast to investigate a murder that may have been committed by a serial killer she's been tracking.

10 p.m., CBS

The Good Wife

Chelsea Handler guest-stars as herself and interviews Peter's (Chris Noth) mistress. Plus, Alicia (Julianna Margulies) represents the firm's senior partner after he is arrested.

11:35 p.m., NBC

The Tonight Show with Conan O'Brien

Conan welcomes 30 Rock's Jack McBrayer—who is just as hilarious and charming in real life as he is playing Kenneth the Page.

Also on the airwaves ...
NCIS, 8 p.m., CBS
So You Think You Can Dance, 8 p.m., FOX
The Biggest Loser, 8 p.m., NBC
Sons of Anarchy, 10 p.m., FX
The Hills, 10 p.m., MTV
The City, 10:30 p.m.,
Styl'd, 11 p.m., MTV

What are you watching tonight?