SIDNEY BRUHL lives in the wilds of East Hampton with his dotty wife Myra and her brown Mercedes. She's very rich; he's written four Broadway flops. She screams when the telephone rings; he's snide, dry, urbane and British. She has a weak heart; he collects antique instruments of destruction. And they don't get along too well either. It all seems so obvious.

But hold on a minute. This is comedy-thriller and we're still in act one. Some master plotting is in order here--bizarre reversals, wacky characters, things going bump in the night. After all, Myra (Dyan Cannon) may be a bit too touchy/feely for her husband's effete tastes, but has-been Sidney (Michael Caine) would never murder her--he needs an ego-booster, not the missus's millions. Or does he?

Enter, stage right, the young and oh-so-handsome Clifford Anderson (played by the young and oh-so-handsome Christopher Reeve), an aspiring playwright and adoring former student of Sidney's at Stonybrook. Clifford has written a play called Deathtrap, a sure-fire smash which turns his professor green with envy, and he brings it to the Hamptons for some polishing up. He also brings his outline and all his notes. No other copy of the play exists (the xerox is "on the fritz"); he lives alone; no one else has read his incipient masterpiece. Maces and daggers loom ominously from the walls, Sidney's eyes begin to gleam, and again things seem obvious.

But in Ira Levin's clever drama, things are seldom (if ever) what they seem, at least not for the first hour or so. It would be criminally unfair to those who haven't seen Deathtrap in either its play or movie form to reveal much more of the plot. Suffice it to say, reversal builds on reversal, a persistently wacky character arrives on the scene in the shape of, of all things, a Dutch psychic named Helga Tendorp, and things not only go bump in the night--they also scream and menace various characters with blunt objects.

BUT too often Deathtrap looks like a film version of a staged performance, so self-consciously theatrical is Lumet's direction. The play was so successful in the theatre, that Lumet can't really be blamed for borrowing some of its techniques for his film. The Bruhl's Hampton home looks lovely with its woodsy interior but it also looks stagey. Doors, windows and a spiral staircase are too neatly arranged around the sides of the set; by shooting rooms up from the floor and down from the ceiling Lumet adds a closed-in effect that verges on the claustrophobic. This may be intentional--a kind of tribute to the play within a play within a play-ness of the plot. But this Deathtrap is also a play within a play within a movie, and staginess just doesn't look right.

In general, Lumet allows himself too many flashy camera angles, too many close-ups of ecric, murderous eyes. At several instances, the camera tracks someone's face as he speaks walking in circles around the room. This is dizzying to watch and doesn't seem to serve any purpose. Tracking feet around the room also seems a contrived and self-conscious maneuver, but Lumet gives us a healthy dose of this too.

DEATHTRAP BEGS to be compared to Anthony Shaffer's Sleuth, another closed-room, twist-filled thriller, and unquestionably loses out in the comparison. But with intricate plot twists (which unfortunately tend to fizzle toward the end), and some snappy dialogue, it makes a fair attempt at matching the wit and elegance of Shaffer's play. Tendorp, the psychic, adds a nice comic touch by dropping by to see Sidney at all the wrong times, and prophesying ominously about a dangerous playwright named "Smith-Collona." Cannon is suitably daffy as the gushing Myra, and Reeve is, well, a hunk. Caine, who played Reeve's younger man to Laurence Olivier in Sleuth, undoubtedly steals the show. Biting and demonic one moment, vulnerable and pitiful the next, he's really the only actor in the movie who takes his character beyond the traditional two-dimensionality of comedy-thriller.

All in all, Deathtrap is enjoyable, if easily forgotten. That its advertisements feature a giant rubik's cube probably says a lot about the film. You might not guess its first few moves, but once on your way things seem to get more and more obvious. A pleasant experience, if not a lasting one. And the novelty soon wears off.