The Legend of Barney Thomson is the directorial debut of actor Robert Carlyle, and it’s one of those black comedies about a serial killer in which, as the bodies pile up, plausibility edges closer and closer to the window until it flies out completely. (No. Wait. Come back! I’ll massage your feet!) This wouldn’t, in fact, matter at all if there were something else to hang onto; if the characters were involving, or the story was told with wit, zip and panache, but it just monotonously drones on.