Pentonville Prison Wally Hubbard is serving a long sentence for arson But after befriending & tricking one of the officers Hubbard makes an audacious escape Inspector Marmion the detective who arrested Hubbard is warned to watch his back but it seems that Hubbard has another target in his murderous sights However the investigation is mired in confusion the identities of killer & victim become increasingly ambiguous An inmate at an internment camp who might be a spy sending intelligence to the Germans complicates matters further & the multiplying manhunts as well as Marmion's concern for his injured & withdrawn son Paul leave the detective desperate & perhaps with too many threads to untangle