France 1944 and in a secret camp men prepare for a daring mission. The unusual thing is that they are German soldiers who will masquerade as U.S. troops in order to cause confusion and buy time for a last gasp German Offensive. Later,five U.S. G.I.'s travel toward the front lines and begin to suspect each other of being a German infiltrator.

A sinister plot to destroy the U.N. by a series of calculated assassinations is discovered.

The intrepid pair, Lt. Lacy and newspaperwoman Karen Lownes, are out to save the United Nations from potential assassinations.