Evil Under the Sun is an unexciting novel, even by Agatha Christie's genteel standard; it completely lacks the dark twists of, say, ''The Mirror Crack'd,'' which was the last Christie puzzler to reach the screen. Diehard fans of the genre are sure to enjoy the modest virtues of the new ''Evil Under the Sun'' movie, which includes another portly performance by Peter Ustinov -- as the ratiocinative Hercule Poirot solving the murder of a beautiful woman -- and a summery ambiance in which ''sun'' pleasantly outweighs ''evil.'' Still, the plot is low on thrills, and the attempts at campy humor fall flat.
One nice thing about ''Evil Under the Sun,'' however, is that it brought James Mason to the United States for a promotional tour, during which he discussed his long career in British and American movies. Over lunch the other day, he reported to me that filming ''Evil'' was great fun, with an all-star cast -- Maggie Smith, Diana Rigg, Roddy McDowall, even Sylvia Miles as Mason's wife! -- gathered for several weeks in balmy Majorca. It became so pleasant, in fact, that periods of work started to seem like intrusions on the real business at hand, which was soaking up the surf and sun. Apparently everyone was a little sad when the last scene was finally wrapped up and it was time to head back to reality.
A nonbeliever in ''method'' acting, Mason nonetheless adheres to the value of research and steeping oneself wholeheartedly in one's role. A few weeks in Majorca sound like a most pleasant manner of accomplishing those goals, and at least one suave British actor seems to have enjoyed the stint thoroughly.