THEATER REVIEW : Oh, What a Tangled Web : Despite some interesting twists and turns, ‘Promises to Keep’ slips up with a dissatisfying conclusion.

Before he lets it unravel, Ido Dooseman seems to be on to something in his new play, “Promises to Keep,” at the American Renegade Theatre.

Not a mystery, not a whodunit, Dooseman’s drama truly keeps you guessing where it’s going next. His puzzle piece is based on the simple premise that once you alight on the slippery slope of lies, there’s no telling where you’ll end up.

In fact, the web of lies involving brothers David (David Beckett) and Jim (Barry Thompson) becomes so baroque that we’re never quite sure of the truth--perhaps Dooseman’s best playwriting trick.

Unfortunately, tricks in the form of twists and dramatic U-turns are all that “Promises to Keep” ultimately amounts to; that, and some very tired observations about sibling rivalry.

It could have been so much more. Things start clumsily, but the moment Jim steps inside the San Francisco apartment of David and his wife, Julie (Lea Anne Wolfe), a sense of absurdist danger a la Harold Pinter is in the air, and Thompson’s brooding, pent-up nervousness only makes the air heavier.

Jim is alone for this dinner date, without his wife, Barbara, who apparently has a migraine headache. Actually, that’s not true, Jim says (making the first of a few of these admissions). Barbara’s dead. I killed her, he admits.

But did he? David seems to believe him. Jim confesses to his brother on the condition that David won’t tell Julie. But because he believes Jim so much, and doesn’t make it a practice to hold things from his wife, David finds this a difficult promise to keep.

A slippery slope, all right, but Dooseman slips himself. The playwright’s strategy equates murder with breaking a promise, and determines that notifying authorities about a murder is worse than not doing so because it amounts to a betrayal.

The problem is that Jim changes his story so often that we’re never sure if there’s method to his madness or simply madness. He does push David into an emotional corner, though, which is what he seems to have wanted all along.

Better an absurdist game than what “Promises” actually becomes: one self-hating brother’s revenge (Jim’s) on a brother (David) who’s always had things his way. Even Thompson, an actor with a talent for mercurial moods that are always slightly off-center, loses some of his grip during the play’s melodramatic finish.

Until then, he holds director Matt Kirkwood’s sputtering staging together; his co-stars Beckett and Wolfe are as stale and uninvolving as he is magnetic.

Everyone, though, is undone by a literal-minded conclusion, which, in a play about the morality of betrayal, is the biggest betrayal of all.

WHERE AND WHEN

What: “Promises to Keep.”

Location: American Renegade Theatre, 11305 Magnolia Blvd., North Hollywood.

Hours: 3 p.m. Saturdays and Sundays. Ends Jan. 29.

Price: $5.

Call: (818) 763-4430.