Heavily padded chase action--as Nazi spies try to penetrate the Los Alamos A-bomb project. Captain Stefan Roebling, a former German commando with a bad leg, is transfered to the Abwehr and assigned to the mysteriously murky Prometheus Operation: he sneaks into the U.S. by murdering an alcoholic diamond-smuggler and stealing his identity. And in Washington he falls in with Nazi agent ""Martha,"" the wealthy Dane Mrs. Erika Huntington, uncovering a lead which eventually directs him to the Los Alamos site. But, as Roebling begins to question his ever-puzzling orders, he realizes that he's been set up (by a jealous Nazi officer) to be the fall guy in a code-stealing plot; and indeed, when he and agent Erika become lovers (he has forced her to come along on the trip to Los Alamos), she confirms this treachery--he's meant to be caught! (He's even been given obviously counterfeit U.S. money.) So Roebling hatches a plan of his very own--to wipe out the Los Alamos project, not by blowing up the reactor but by assassinating the whole crew of Jewish atomic scientists while they're at their synagogue on Friday evening. Counterpointing Roebling's moves toward this goal is the clue-tracing of Captain Gregory Allison from the Counter-Intelligence Corps--and finally there's a face-to-face showdown. . . with Roebling wielding a plastique bomb at the crucial moment. Dull, standard thriller action, particularly bereft of period color or detail.