There are not too many shows -- except the bad ones -- that can claim to be at their best when the stage is blacked out. But Trinity Players' production of Frederick Knott's "Wait Until Dark" is at its suspenseful height when the lights are dim.

As a blind woman grapples with a murderous criminal, it is light that is the enemy. With each glimmer her advantage dwindles, as she is at her best in the darkness -- her familiar world.

"Wait Until Dark" is no top-of-the-line classic thriller. The plot is not brilliant, the lines not chilling, the characters not enormously engaging. But it will make you occasionally grab the arms of your seat, sweat a little and wonder nervously what happens next -- a solidly workmanlike endeavor in content and execution.

The action focuses on a child's rag doll that is stuffed with a fortune in heroin. Naturally, all sorts of baddies want it. But it's somewhere in the house of Sam and Susy Hendrix, who unwittingly come into possession of the doll when a woman on an airline flight asks Sam to deliver it to a sick child. The doll gets lost, and the rest of the play is about the search for it.

A trio of nasties concocts an elaborate scam to get the doll away from the couple, which involves sending Sam on a wild goose chase and leaving Susy alone to deal with the killers. They trick her into thinking Sam is an adulterer and murder suspect. Having recently lost her sight in an accident, Susy is still bitter about her blindness and a little helpless. She loses that weakness fast as she unravels the dirty doings and must think fast to save her own life.

Making sense of all of this is hindered slightly by the stiff direction of Constance Kulik, who doesn't seem to be able to gracefully move her characters around the stage.

There are rays of brightness, though. Elizabeth Stark Dugan's Susy is sweet, courageous and whiny at the same time, making her a realistic heroine. If played incorrectly, she could appear unrealistically heroic. As her nemesis Harry Roat, John Edward Brady at first seems a little too much, but manages to get creepier as the play progresses. And Jennifer Albright's turn as a bratty little girl who becomes a mini-heroine is delightfully difficult. The rest of the cast is good, though not memorable.

The set is only adequate, though the lighting, an important component, is always professional. Although the play does not leave you on the edge of your seat, it nudges you there. And when the set is finally brightly illuminated at the show's climax, you wish for the shadows -- a clever manipulation by playwright Knott, who forces the audience to see evil in the light and find solace in the night.

"Wait Until Dark" plays at the Trinity Theatre, 3514 O St. NW, at 8 p.m. tomorrow and Saturday. For information, call 965-4680.