Attempts to solve the mystery surrounding the loss of his destroyer HMS Fortune, along with the complete Royal Navy convoy HXL 267, in September 1943, leads Commander Bob Garner into even more dangerous waters than those of the North Atlantic. Although exonerated of blame, he is dismayed that his superiors do not accept his report that the convoy was attacked by an exceptionally fast submarine. There also seems to be an unwarranted secrecy about the purpose of the defeated convoy. Traumatised by the loss of the Fortune and the lack of reaction by his superiors, he finds his personal life in turmoil and wife Lissa unable to cope with his state of mind; his only solace in the form of Mary Forbes, a sympathetic Wren officer. Meanwhile the captured Frigatten Kapitan Hinterberger seems to know about the sinking of the British convoy, but teases Bob Garner, holding back on any real information. As the truth unfolds regarding the loss of convoy HXL 267, the war service of German Kapitan Hinterberger, the secret of the high speed submarines and the purpose of 'Operation Cloudburst', Commander Bob Garner shares his place on the stage of history with figures such as General Eisenhower, Adolf Hitler and Gross Admiral Doenitz, who led the U boat campaign, together with double agent Garbo and the mysterious Committee XX.