Collins, a veteran of comic-strip (Dick Tracy) and paperback (the Nolan series) suspense, makes his hardcover debut with a routine but affable hard-boiled outing--as youngish narrator-hero Mallory, ex-cop and would-be mystery writer in Iowa, tracks down a local house-robbery gang. Mallory, you see, has a personal interest in the case: the latest robbery victim, old Mrs. Jonsen, died of a heart attack during the heist--and she was one of the senior citizens to whom volunteer Mallory delivered hot meals from the local hospital. Furthermore, the bad guys keep kicking Mallory in the ribs. And so Mallory insists on giving the cops a hand. . . while the clues also lead him to an old high-school flame with a shady estranged husband. True, the exposure of gang members--which follows more heist attempts and Mallory's perilous journey in the bid guys' van--involves only the most hoary sort of surprises, and Mallory occasionally waxes pretentious and/or adolescent. But, for the most part, the narration here is jaunty, curt, modestly amusing--and, if Collins can come up with fresher plots than this one, Mallory could become a welcome addition to the wry, tough amateur-sleuth brigade.