The actress Mary Astor (1906-87) is likely best remembered for her performance as the shifty client of Sam Spade in director John Huston’s adaptation of Dashiel Hammett’s “The Maltese Falcon” (1941). Why shifty? Because this femme fatale came with two noms de plume: Ruth Wonderly and Brigid O’Shaughnessy. The logic behind the ruse is of a piece with this, among the most convoluted of detective yarns. The picture is best savored for the chemistry between its actors and the tart dialogue. Asking too much sense from some things misses the point.