It is late Summer 1944 and the Nazis have unveiled the first of their secret weapons. As V-1s packed with explosives drone high across the Channel and V-2s crash out of the skies on a defenseless Britain, the Allies wonder what other weapons might soon imperil their war effort.

A new threat is discovered by Ian Moore, the Squadron’s charismatic leader, who has survived his crash in the Loire River but spent weeks in a German hospital where he has heard enemy crews boasting about a new weapon. Urgently needing to know more, London uses foreign partisans and the Squadron to free him. On Moore’s return to England the Allies discover the danger is so great that it must be eliminated whatever the cost.

Created to perform such demanding one-off missions, 633 Squadron is given the task. But where is the weapon being developed? Davies, ruthless with his Squadron and his agents when a situation demands it, sends the courageous German girl, Anna Reinhardt, back into enemy-occupied Europe to find out.

What the weapon is and how it is destroyed in spite of its apparently impregnable location is told in this latest chronicle of 633 Squadron in which the author explores with his customary flair the characters, skills, and daring of the airmen he created in the first of these famous novels and has so successfully developed in the whole dazzling series.