Tonight's best bets
• "CSI: Crime Scene Investigation," 9 p.m. on CBS. Grissom (William Petersen), Catherine (Marg Helgenberger) and the other CSIs investigate a spree of brutal Vegas tourist beatings that take place within a few hours of each other. One of the victims is left for dead and another is beaten severely. While following the trail of evidence, Greg (Eric Szmanda) interrupts a third beating in progress; by saving the victim, Greg himself is severely injured and faces a decision that could impact his entire life. This episode features the TV acting debut of Kevin Federline.
• "Supernatural," 9 p.m. on The CW. Fan universes collide tonight as "Buffy the Vampire Slayer's" Amber Benson guest stars on this new episode of "Supernatural." Sam (Jared Padalecki) and Dean (Jensen Ackles) meet Gordon (guest star Sterling K. Brown), a fellow demon hunter who has been systematically killing vampires in a small town, and Dean immediately bonds with the older man. But once Sam meets with the lead vampire (Benson) - and discovers they are actually peaceful creatures who survive on cattle blood - he decides not all supernatural beings are evil and forces Dean to choose sides.
• "Six Degrees," 10 p.m. on ABC. While Whitney (Bridget Moynahan) plans her wedding, Laura (Hope Davis) wonders whether her friendship with Whitney can survive telling her the truth about Roy (guest star Jonathan Cake). Carlos (Jay Hernandez) and Mae (Erika Christensen) go on a double date to a karaoke bar with Damian (Dorian Missick) and Regina (guest star Zoe Saldana), and Damian realizes Mae's connection to him.
• "Good Morning America," 7 a.m., ABC: Director Barry Levinson ("Man of the Year"); author Moll Anderson ("Change Your Home, Change Your Life").
• "Martha," 9 a.m., KONG: Andy Dick carves pumpkins with Martha.