Germany, 1942: a team of American commandos—infiltrator Earl Hollister, wheelman Roy Warner, demolitions expert Joe Morris, and sniper Bill Riley—sneaks into a Nazi armament factory, plants explosives, and makes their getaway. Shortly thereafter they are informed they are taking on a new recruit, a hero in a symbolic red-white-and blue costume to rally the folks back home. The commandos are ordered to take the new man on a routine mission to destroy an enemy supply route to give him some actual field experience. The resentful GIs snub the new guy, offended at having to baby-sit a raw recruit whose garish costume will only draw enemy fire. That night, the parachute behind enemy lines and plant explosives on the bridge—but it turns out to be a trap and Nazi tanks roll in. The new man hurls his shield to hit the enemy commander from behind; the blow only annoys him and he orders his troops to fire on the brightly colored American. The distraction gives the team the opportunity to seize control of a tank and fire on the others. The rookie gets hold of his shield and clobbers the Nazi holding a gun on them and the others take the Nazi soldiers prisoner—but then a massive battle tank commanded by Baron Strucker forces them to surrender….
The Americans are imprisoned in Hexenhammer Castle where they blame one another for their capture. The bickering is a ruse, however, to trick the guards into coming close enough to be overpowered. Elsewhere on the premises, Strucker is showing the remarkable shield to top scientist Johann Schmidt who begins to suspect that its wielder is a product of the Americans’ sabotaged super-soldier project. At this point the Americans burst into the room, guns blazing. As the commandos exchange fire with the Nazis, the super-soldier pursues Schmidt through a secret doorway and down into his underground lab. Schmidt reveals that he is the first recipient of the German enhancement program and is more than a match for his inferior American imitator. The two super-soldiers fight, with Schmidt gaining the upper hand when suddenly the Nazi is felled by a burning sensation in his body. Before the hero’s horrified gaze, Schmidt’s face burns itself into the grisly semblance of a red skull and he collapses to the ground. Upstairs the Americans have been captured by the superior numbers of the Nazis but suddenly the shield-slinging hero enters throwing punches; his appearance gives the captives the edge they need to overpower their captors and the hero manages finally to hurl the shield with enough force and accuracy to deck Strucker. The hero informs them that he has set the timer on explosives in the lab and they have only a few minutes to get to safety. As the castle explodes behind them, they congratulate each other on their teamwork while wondering what they should call their new partner….
A short time later, the newspapers herald the advent of a new hero—Captain America…