"Evil Under the Sun," a movie version of one of Agatha Christie's moldier showcases for Hercule Poirot, is too stilted to arouse anything as dreadful as evil. However, the sun does shine enviably upon the Majorcan locations. When the foreground isn't cluttered with overstuffed museum pieces like Peter Ustinov--indulged an encore as Poirot after demonstrating that Charlie Chan really suits him better--the film offers balmy, soothing scenic diversion.

The murder site, originally a summer resort on the southwest coast of England, has been transposed to a secluded private spa in the Mediterranean. Christie had placed Poirot casually among the vacationers. In the movie he's identified as the agent of an insurance company actively pursuing a dubious claim about a precious gem. This preliminary case leads him to the resort, where homicide awaits a vain, bitchy, man-eating theatrical star named Arlena Stewart Marshall, whom every other guest might want to strangle.

In fact, the victim appears to provoke or justify such universal hatred that mass execution along the lines of "Murder on the Orient Express" logically springs to mind. Christie had another solution up her sleeve, but the movie may suffer from the fact that it tends to recall "Death on the Nile," where Ustinov made his debut as Poirot. Moreover, the filmmakers haven't been able to finesse the self-evident fact that only one of the suspects has much of an opportunity to throttle Arlena. The mystery consists of misleading clues designed to obscure this fact until the denouement.

Striving to take up needed tucks in saggy material, screenwriter Anthony Shaffer tends to overcompensate by severely reducing the cast of characters while camping up their repartee.

Christie's stock company of suspects may creak as audibly as The Tin Woodman, but it doesn't necesssarily help to streamline her technique when the streamlining amounts to narrowing the range of suspects and intensifying the level of artificial chitchat. "Murder on the Orient Express" and "Death on the Nile," the initial Christie adaptations from the same team of British producers, John Brabourne and Richard Goodwin, seemed to appreciate the theatrical effectiveness of respecting her devices, even if it risked a little mustiness and literal-mindedness. With "The Mirror Crack'd" and now "Evil Under the Sun" they seem to be selecting less astutely from the Christie backlog and then aggravating this misjudgment by jollying the flimsy material into shreds.

For example, one conspicuous reason it becomes difficult to associate anything evil with this case is that Diana Rigg as Arlena is obliged to exchange an excess of backbiting conversation with mock-antagonists like Maggie Smith as the proprietor of the hotel and the preposterous Sylvia Miles as the gruff spouse of a Broadway producer (James Mason). An excruciating line reader, Miles suggests maybe Miss Rona filtered through a drunken, gravel-throated medium. Overdosing on trite bitchiness, Shaffer also invents a role for Roddy McDowall as a swishy, gossip-hungry celebrity journalist named Rex--the ostensible period is the '30s and he's alleged to be a New Yorker staffer--avid to publish a biography of the notorious Arlena.

Like a lot of writers who fail to fool the subconscious, Shaffer can be detected apologizing for the missing verbal sparkle. "Why don't you go play with yourself?" someone demands of the McDowall character, prompting the reply, "Is coarseness a substitute for wit?" Evidently not, judging from the dialogue in "Evil Under the Sun."