Grey Wolves (Henderson's Boys Series #4) in Bloomington, MN

Spring, 1941.
German submarines are prowling the North Atlantic, sinking ships filled with the food, fuel and weapons that Britain needs to survive.
With the Royal Navy losing the war at sea, six young agents must sneak into Nazi-occupied Europe and sabotage a submarine base on France's western coast.
If the submarines aren't stopped, the British people will starve.