Time Out says
Like the Bob Hope movies which it alludes to, Manhattan Murder Mystery is as light and brazenly generic as Allen's early work. As a result, it is both unusually insubstantial, and, at least in the second half, extremely funny. Hope-like in his panicky cowardice, Larry worries not only about the feelings of his wife Carol (Keaton, refreshing) for his old friend Ted (Alda), but about her determination to investigate the death of a neighbour. At first, Larry thinks Carol is fantasising, but then he starts to witness strange events. Cue to a fast, ramshackle, thrill comedy as entertaining as it is removed from the realities of contemporary New York. A movie inspired by movie escapism. Minor, but surprisingly, almost defiantly upbeat.
Cast and crew