It takes a special sort of courage to serve in midget submarines, and Lieutenant David Seaton, commanding officer of XE16, needs no reminding of the perils involved. The little X-craft with their four-man crews have been used against heavy enemy surface units and important harbor installations.

But in 1944, with the Allies poised for an invasion through France, a new and more hazardous role is given to Seaton’s flotilla.