Norwegian underground leader Erik Bergman reports to British authorities the location of a German V2 fuel plant. The plant is in an impregnable location — beneath an overhanging cliff at the end of a highly defended fjord. The only way the British can hope to destroy the plant is by collapsing the cliff on top of it. In order to do that, light Mosquito aircraft must be utilized. This is the job assigned to Wing Commander Roy Grant's 633 Squadron. In order to assist Grant in his air attack, Bergman attempts a simultaneous ground attack, but the ground attack fails, and Bergman is captured by the Germans. When he is tortured in their efforts to uncover the RAF plans, Bergman may not be able to withhold the top-secret information.