CBS and Fox take advantage of a summer Friday night to showcase a couple of television’s more promising shows. “Veronica Mars” (CBS) isn’t even on CBS; it’s a UPN drama. Viacom owns both networks, and they clearly think exposure on the more established network will draw fans to the drama starring Kristen Bell about a teenage detective toiling in a dark town of secrets and lies.

In the show’s pilot episode (7 p.m.), Veronica avenges a new kid who had been duct-taped to a flagpole by a gang of bullies. In the second helping (8 p.m.), the high school Sherlock takes on the case of the missing poker pot. CBS’s Friday night trip to “Mars” continues next week with two more episodes.

¢ Sometimes even the most overused journalistic cliches ring dreadfully true, and tonight “Dateline” (7 p.m., NBC) looks at a story that qualifies as “every parent’s worst nightmare.” It also shows how some of society’s worst problems can occur in “the nicest homes.”

Thom and Deirdre Forbes, both 52, are bright, sensitive people who met at the New York Daily News when he was an editor and she was a photographer. They live in a big house filled with books in a safe, lovely suburb. Their daughter, Carrick, was a beautiful baby and a bright child, but she recoiled from schoolwork and was quickly deemed a problem student with learning disabilities. Her drug use probably began with adolescence and only worsened when she dropped out of high school.

Using home videos and professional camera crews, “Dateline” followed the Forbes as they try to cope with their daughter’s heroin addiction and her flight to New York’s drug-dealing demimonde while trying to protect their younger son from her influence. The Forbeses also fear that they may have passed along their own predisposition for substance abuse to their child. Thom and Deirdre used to drink heavily but have entered recovery. And both come from families with histories of addiction. Just where do a parent’s responsibilities begin and end when heroin takes control of a loved one? Can you be too supportive of an addict? Too tough? The answers don’t come easily.

Tonight’s other highlights

¢ Country relatives come to visit on “That’s So Raven” (7 p.m., Disney).

¢ Only math can stop a virus on “Numb3rs” (9 p.m., CBS).

¢ Sandra Bernhard guest stars on “Crossing Jordan” (9 p.m., NBC).

¢ Scheduled on “20/20” (9 p.m., ABC): an interview with Lynda Carter.

¢ Comedian D.L. Hughley becomes talk-show host with the new weekly series “Weekends at the D.L.” (10 p.m., Comedy Central).