Friday Night for 3 Geeks and a Creep

NBC and Fox attempt to sweep viewers into their respective corners with series finales.

Using the ratings as a yardstick, one of these dramas will return next season. The other may not.

The show on firmer footing is “Law & Order: Special Victims Unit” (10 p.m. NBC), which completes its second season with a grisly episode about a knife-wielding murderer who mutilates four victims within 24 hours.

Richard Thomas, who was very persuasive as a serial killer on “The Practice,” must have relished that unsettling experience. Here he’s equally convincing as the prime suspect, a sick and extremely creepy family man charged with the bloody crimes. Karen Allen (“Raiders of the Lost Ark”) makes a welcome prime-time appearance as his long-suffering wife.

“The Lone Gunmen” (9 p.m. Fox), that amusing and elaborate but always improbable “X-Files” spinoff, is the hour on thin ice. Since settling into a Friday slot (once occupied by “X” itself), those bright yet bumbling hackers Byers (Bruce Harwood), Langly (Dean Haglund) and Frohike (Tom Braidwood) have attracted a meager audience. If they fail to deliver again tonight, it’s probably back to guest spots opposite Gillian Anderson.

In the cliffhanging finale, the Gunmen discover a government document that could provide the answer to every conspiratorial question they’ve ever asked. Or it could get them killed along with the exotic beauty Yves (Zuleikha Robinson), who may be linked to a covert group of assassins.

Typically, these obsessive guys are in over their heads, going to great lengths to crack complex codes and thereby seek the truth out there.

As guest star Michael McKean puts it halfway through the episode: “You guys never went to your high school prom, did you?”