For her last waltz with Roderick Alleyn, the late Ngaio Marsh went back to the theater--site of many of her best (and some of her weakest) mysteries. And this swan-song is a sequel, in fact, to Killer Dolphin (1966), with director Peregrine Jay of the Dolphin Theatre now directing Macbeth--that notoriously ill-fated play, bearer of dozens of backstage superstitions. Can director Jay persuade his cast to forget the omens and get on with the work? Not likely--since there are grisly practical jokes going on, plus the rumor that the boy playing Macduff's son is the real-life son of a convicted psycho-killer. And though the production shapes up beautifully, a few weeks into the run the actor playing Macbeth is actually decapitated--his bloody head brought on instead of the papier-machÃ‰ prop at the finale! Whodunit? The most obvious person, alas. Nor does Alleyn do much here in the way of sleuthing. (The murder doesn't even occur till 2/3 of the way through.) But those who share theater-woman Marsh's love of the stage and Shakespeare in particular won't mind too much: the rehearsal process is richly detailed; the backstage tensions are shrewdly framed. And though this last Marsh is far from a great mystery, it has what many of her fans always prized most: wit, charm, and oodles of atmosphere.