American GI Ernie Williams| admittedly weak-kneed| has an uncanny resemblance to British Colonel MacKenzie. Williams| also a master of imitation and disguise| isasked to impersonate the Colonel| ostensibly to allow the Colonel to make a secret trip East. What Williams is not told is that the Colonel has recently been atarget of assassins. After the Colonel's plane goes down| the plan changes and Williams maintains the disguise to confuse the Nazis about D-Day.