The trick to creating a good, solid mystery story is as much a matter of timing as its about plot contrivances, colorful characters or surprising twists. Anyone who has ever labored in frustration with an un-finishable Sunday New York Times crossword knows that any puzzle that takes too long to solve ceases to be any fun. The best murder mysteries, be they on film or in print, are slight affairs that get to the point, spell out their clues, line up their suspects and, hopefully, zap us with a few surprises; being complicated without being unduly confusing. And they play fair; on second, third and fourth viewings of the clues and red herrings we should be just as pleased to marvel at how well it all comes together as we were at being surprised in the first place. Indeed, good thrillers should get better on repeated viewings as we anticipate the double and triple crosses.<br /><br />Sidney Lumet's comedy-thriller DEATHTRAP, as derived from Ira Levin's hit Broadway play, is a great example. It moves along at a tidy clip, skillfully juggling its clues, being (almost) totally honest with us (even when it is lying to us) and yet never revealing where it is going (even when it is telling us where it might go). It is less a murder mystery movie in the traditional vane than it is a movie about murder mysteries, derived from a play about playwriting. Rather than going backward -- a murder and then an investigation to explain why everything happened -- DEATHTRAP leads us through the crime(s) step by step, leaving ample room for the unexpected; as the ads advise it is less a "whodunit" than a "who'lldoit." <br /><br />DEATHTRAP is often compared (unfavorably, oddly enough) to the play and movie versions of SLEUTH, though in reality it has much more in common with SCREAM, the self-mocking essay on teeny-bopper horror flicks. Like that clever film, DEATHTRAP labels itself (a thriller about thrillers), sets it parameters ("a one-set, five character moneymaker") and then proceeds to deconstruct its genre by revealing itself as "the most outlandish and preposterous set of circumstances entertaining enough to persuade an audience to suspend its disbelief." <br /><br />DEATHTRAP bravely gives us a mystery with only five major characters, two of which are of minimum importance. Henry Jones as a cagey lawyer is on hand mostly for exposition (and to supply us with his penchant for folksy charm) and Irene Worth is all quirks and comic relief as a psychic-cum-sleuth who acts as the nominal detective. That leaves three main characters to be the killer(s) and/or the victim(s): It is a testament to Michael Caine's abilities that as Sidney Bruhl, a down-on-his-luck author of mystery plays, he creates a character who we intrinsically like and trust, even as we recognize immediately that almost everything he says is a lie. As his adoring, if somewhat ditzy wife, Myra, Dyan Canon flirts with being over the top by giving a roller-coaster ride of a performance with a character that by turns seems to be frail or overbearing, crafty or hysterical, timid or bold and uncompromisingly in love with a less than reciprocating Sidney. The third angle of this unexpected triangle is a fledgling playwright named Clifford Anderson played by Christopher Reeve in such a way that we never quite get a handle on just who his character is: enthusiastic preppie wannabe writer, semi-innocent victim or cunningly charming sociopath. As the various character dance around each other, the cleverly dour script adapted by ace scribe Jay Presson Allen manages to be consistently amusing, even as it builds suspense. And even after the final twist (an improvement over the play's finale), it may not be quite clear just who has manipulated who to do what.<br /><br />Lumet is by no means a master of comedy, so he lets his able cast have free reign to flesh out the characters and they all give sharp, theatrical, yet subtle work, with Reeve being particularly noteworthy. But what Lumet does so well is to work skillfully in tight quarters. As he did brilliantly in 12 ANGRY MEN, he takes a one-set play, and with a minimum of opening up, manages to make what could have been cramped, stagy and stagnant seem endlessly photogenic and spacious. The setting, a country home converted from an old windmill, is relatively small, but as designed by Tony Walton it manages to be both cozy and charming, as well as spooky and treacherous. It is so truly difficult to tell where the studio set and the real country house cross boundaries that to a degree the set becomes a sixth character. And as the scene of the crime, it is a most inviting deathtrap indeed.