After the crushing defeat of D-Day, Germany had resorted to launching so-called vengeance weapons to terrorise the British. In response, Helen McGrath of the SOE and Captain Tim Lidster of the OSS, had been tasked with tracking down the architect of the latest portable V1 launchers – Major Walter Himpel of the Luftwaffe. Little did they know, their mission would prove to be far more than they bargained for, Himpel had a much more diabolical plan in mind - one that would target the mainland of the United States!