Science reporter Delaney, on a lend-lease assignment in London for the magazine View, identifies a man fished out of the Thames as the nuclear physcist Rayner and suspects a dangerous impersonation as another man continues as Rayner at an atomic research installation. The radication fogging of his photographs, and the aplastic anaemia of the hospitalized Rayner confirm Delaney's hunch that the patient is the isotope man- and while the police tick him off time and again- he carries on his independent investigation at a lively clip.... Straddling the mystery- s.f. barrier, this is an alert and easy form of entertainment.