"Empty Nest" (8 p.m., Ch. 2) gets an A for its intentions tonight but a D- for execution.

This silly sitcom attempts unsuccessfully to get rather serious tonight with an episode about kids and guns. Dr. Harry Weston (Richard Mulligan) treats a young boy for an ulcer - an ulcer brought on by the stress of being threatened at school.Harry's solutions are simplistic - he'll talk to the kids; he'll talk to the principal. The youngster's solution is sadly more practical - he gets a gun.

Without giving the entire plot away, Harry ends up getting shot accidentally with that gun in an incredibly clumsy, unbelievable scene.

And, unfortunately, the entire episode is clumsy and unbelievable. Not to mention trite.

Again, the folks at "Empty Nest" undoubtedly had the best of motives. But this strange episode doesn't really help dramatize the problem of kids and guns, it trivializes it.

They'd be better off going back to just plain silliness.

- When "Babylon 5" premiered last year as a two-hour movie, it was great to look at but dull and ponderous.

The sci-fi show returns as a weekly series tonight (7 p.m., Ch. 14), and while the special effects are still marvelous, the pace has picked up and the show appears headed for syndicated success.

The series, set 200 years in the future, revolves around a huge space station where the various powers in the known galaxy meet to try to resolve their differences without war. And that's put to the test in the premiere, when a Centauri outpost is attacked by one of the other powers.

There's plenty of action, and the basis for an interesting series is set.

It's not without problems, including several wooden performances - particularly a stone-faced Michael O'Hare as the station's commander.

But sci-fi fans will want to tune in.

It's about time we had a vision of the future that didn't spring from the "Star Trek" universe.