An uneven police procedural with a New Zealand background. Constable Joe Blaney is found shot dead in his apartment--just after taking part in an elaborate fake bank-holdup for ""Ponderosa Day""--and holding the fatal Luger is Tommy White, retarded son of Professor White and his artist wife. But when inspector Jonas Peacock and Detective-Sergeant Steven Arrow interview Tommy's parents, Tommy's elderly pals, and Blaney's bitchy girlfriend, they soon suspect that Tommy is hardly the villain here. And indeed Tommy himself then dies by drowning--and the cops zero in on the motives in the two cases, both of which are buried deep in the past; meanwhile, too, there's the matter of a cop being framed for a series of senseless robberies. Mantell, unfortunately, makes little of the New Zealand scene. And, though there's some impact and welcome clarification at the windup, jumpy prose and cluttered plotting make this mostly sluggish reading.