That morning in July 1943 still haunted 633 Squadron, for only a single Mosquito made it back from the suicidal but successful Operation Vesuvius. Now, barely a year later, the Germans were once more processing the secret "element" known as IMI in a strongly defended facility in Norway and were about to move their stocks to the safety of Germany. If successful, the whole tide of the war would be turned. Once again, it meant another "mission impossible" for 633 Squadron...