Jensen Ackles and Jared Padalecki, Supernatural Jensen Ackles and Jared Padalecki, Supernatural

9 pm/ET CW
Angels are supposed to be the good guys, right? So why does the heaven-sent Castiel and Uriel want to kill Anna? Sam and Dean finally learn why tonight, but they aren't about to stand around and let it happen. And the angels aren't Anna's only problem. Sinister Alastair and his band of demons are also closing in on her. — Tim Holland

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CSI: Crime Scene Investigation
9 pm/ET CBS
Can people change? That's what Grissom wants to know when he visits serial murderer Natalie Davis, the so-called Miniature Killer, who expertly crafted exact replicas of her numerous crime scenes and left them at the murders for the police to find. He's officially there as part of her transfer hearing to determine if she should remain in a criminal psychiatric facility or go to prison. But his interest in Natalie is much more personal. Yes, Grissom wants to know if an extreme personality like Natalie can change, but the real question he is facing is: Can he change? — Tim Holland

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30 Rock
9:31 pm/ET NBC
Life gets wild and crazy for Liz, especially when she meets eccentric businessman Gavin Volure (Steve Martin, continuing Rock's roll of quality guest stars). Jack and Liz enter Volure's luxury lair for a dinner party, but food isn't the only thing cooking. Volure is spicy hot for Liz — and he also whips up a confidential business proposal for Jack. Meanwhile, Tracy, slipping into paranoia yet again, fears that his children have concocted sinister plans against him. — Dean Maurer

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8 pm/ET CW
Here comes the bride! Chloe and Jimmy have finally come to their big day, but while Chloe should only be worried about things borrowed and blue, she's more concerned that Davis will nip these nuptials in the bud. Trouble comes, however, in the form of Doomsday, who shows up uninvited — how rude! — with designs on the bride. He's not the only unexpected face to appear tonight: Oliver, hot on Lex's trail, travels to Cuba, where he gets a surprising reception from Lana. — Rhoda Charles

For full episodes of Smallville, visit our Online Video Guide.

Celebrity Rehab with Dr. Drew
10 pm/ET VH1
With the reality series Breaking Bonaduce, VH1 learned the lesson that there is an audience out there for celebrities in trouble. Rehab, currently in its second season, continues to prove that maxim with strong ratings. And boy, are these celebs in trouble. It's heartbreaking to see the narrow thread some of the patients are hanging by. Tonight Jeff Conaway tries to leave the program, and tempers flare as Dr. Drew starts getting to the roots of addiction. — Fred Mitchell

For full episodes of Celebrity Rehab with Dr. Drew, visit our Online Video Guide.