I have a confession to make one that could endanger my reputation as a critic. I secretly enjoy “Diagnosis Murder” mysteries. I know I’m supposed to scoff at their obvious plots, predictable pacing and sub-par acting. OK, let’s just call it bad acting. But, those are the very elements that make these old-fashioned television mysteries so irrationally irresistible. For me, watching TV movies based on the old “Diagnosis Murder” series is the video equivalent of slipping into an old pair of shoes. They’re not stylish, but they feel good. Before I know it, I am a paralyzed couch potato whose reptile brain has completely eclipsed my critical faculties. Yes, Dr. Sloane. Whatever you say …

“Diagnosis Murder” regulars Dick Van Dyke, Barry Van Dyke, Victoria Rowell and Charlie Schlatter return in the new feature-length mystery “Without Warning” (8 p.m., CBS). The best thing about “Murder” is that the plot just doesn’t matter. You know that Dr. Sloane and his eager assistants will get to the bottom of the crime.

“Warning” involves a series of deaths at a Mexican migrant farm worker’s camp. The first clues point to a dangerous epidemic. Then, we learn about a nefarious pharmaceutical corporation’s involvement. Anyone who has watched enough of these dramas knows that rich corporate executives are never portrayed as white knights. I won’t give away any more information here, even if the plot really doesn’t matter.

My favorite subplot in “Warning” involves the awkward flirtation between Lt. Steve Sloan (Barry Van Dyke) and a pretty but ambitious tabloid reporter, Ellen Sharp (Kim Quinn). As I have pointed out before, Van Dyke the younger has the beefy physique and wooden style of the late George Reeves of “Superman” fame. As an actor, he makes David Hasselhoff look like Laurence Olivier.

“Warning” also includes many television cliches. Every time we travel to the migrant camp we hear the plaintive plinking of a Mexican guitar informing us that these are a poor, but proud people who won’t be pushed around. Later, as Lt. Steve awkwardly woos Ms. Sharp, the camera repeatedly cuts to a scene of ducks floating in a pond. I wondered, almost critically, “Why a pair of ducks?” But, then my reptile brain asserted itself again, and I was comfortably ensconced in the video cocoon of a “Diagnosis Murder” mystery. Yes, Dr. Sloane, whatever you say … the ducks are fine … Barry Van Dyke can act … I can’t wait for the next installment.

Plot does matter on a very solid episode of “Law & Order: Special Victims Unit” (9 p.m., NBC). After a rich heiress (Mary Beth Hurt) is brutally raped and beaten in her posh apartment, her husband of a few months (Henry Winkler) seems to be just a little too solicitous to be believed. Like the best “Law & Order” stories, this one involves more twists, turns and dead ends than a high-speed chase through Brooklyn. Both guest stars turn in strong performances.

Tonight’s other highlights

Carol Burnett and co-stars Tim Conway, Harvey Korman and Vicki Lawrence reminisce on the repeat of “Carol Burnett: Show Stoppers” (7 p.m., CBS).

As Syd falls for Owen (George Newbern), one of her patients develops a crush on her on “Providence” (7 p.m., NBC).

Wild critters enter without knocking on “When Animals Invade Your Home” (7 p.m., Fox).

Steven Seagal stars in the 1995 action film “Under Siege 2: Dark Territory” (7 p.m., UPN).

A runaway computer virus endangers the world economy in the 2002 thriller “Terminal Error” (7 p.m., Pax) starring Timothy Busfield.

Scheduled on “Dateline” (8 p.m., NBC): people who have reached out to a friend or relative after years of silence.

Crichton’s mind wanders on the third season finale of “Farscape” (8 p.m., Sci-Fi).