Synopsis
Gotham City, January, 1945: Batman and Robin are pursuing the Joker in a wild automobile chase through the city streets. The Jokermobile releases an oil slick that sends the police cars careening off the road but the Batmobile can handle it. Cornered on the docks, the Joker makes his getaway via a spring-loaded ejector seat and a parachute. A quick search of the Jokermobile reveals the odd presence of plutonium…then the Dynamic Duo must leap to safety as the clown’s car explodes. Elsewhere, on the war-ravaged battlefields of Europe, Captain America confronts a massive Nazi war-wheel, a hundred feet in diameter, blazing away with massive firepower. Cap climbs the monster and jams his shield in the wheels, causing the mammoth machine to tip over, allowing American troops to capture the enemy inside. Summoned back to the US, Cap and Bucky are nearing Gotham City when they hear a report of a plane hijacking nearby. Instructing the pilot to fly over the stolen craft, Cap drops out to intercept the other plane, without a parachute. Gunfire from the craft causes him to nearly lose his grip and he is rescued at the last moment by the Batman, descending from his hovering Batplane. Together the two heroes invade the ship and make short work of the hijackers, rescuing the kidnapped scientist J. Robert Oppenheimer. Interrogating the captured thugs on the ground, Batman and Cap are shocked when the men start laughing themselves to death—courtesy of the Joker’s skin patches.
Captain America meets with military brass who explain his new assignment: the Joker is behind a series of thefts connected to the top-secret Gotham Project. Espionage is not his usual game, so it’s clear he is working for someone higher up; the chief suspect: millionaire Bruce Wayne. Steve Rogers will be Wayne’s bodyguard, secretly investigating his ties to the enemy. Steve soon discovers that following a businessman/playboy is a pretty boring duty—until he overhears Wayne telling his ward Dick Grayson about shedding his bodyguard to meet the Joker. Steve tails Bruce to the Wayne Foundation building where he confronts the suspected spy. The two men fight—and quickly recognize each other’s alternate identities by their athletic abilities and fighting style. Batman and Captain America then agree to team up against their common foe.
The Joker reports to his employer, who informs the sinister clown about a certain shipment being made that evening, which the Joker will find useful in a million-dollar blackmail scheme. After signing off, the mysterious boss reveals himself to be the Red Skull. That night, a squad of soldiers is felled by the Joker’s laughing gas, and the villain’s men don their uniforms to hijack the contents of a military transport vehicle. Meanwhile, Batman and Cap have worked out that the object the Joker is after is a prototype atomic bomb, and he is working for the Nazis. The Bat-Signal is spotted in the sky and Cap and Robin answer it, startling Commissioner Gordon. Gordon reports the murders of Shore Patrol members, in a remote location which Cap recognizes as on the route to Washington DC. Batman and Bucky, meanwhile are investigating a deserted warehouse where suspicious activity has been seen lately. Entering they are subdued by the Red Skull’s gas and awaken tied to a hydraulic lift. The lift is wired with explosives set to go off when the lift descends. The Nazi and his henchmen leave and shortly thereafter see the explosion of the warehouse….
Cap and Robin race to the secret airbase where the Joker is loading the stolen atomic bomb on the Red Skull’s transport plane. When the Clown Prince of Crime realizes he has been working for the Nazis, he rebels and the two villains spray each other with their distinctive weapons—to which they turn out to be immune because of their similarity. The Joker is knocked on the head and loaded into the plane, which heads off to bomb Washington. The plane is intercepted by the Batplane—Batman having earlier faked unconsciousness and was able to escape his bonds and free Bucky—carrying the two heroes and their sidekicks. The Batplane grapples the Nazi craft and the heroes invade and seize control of the plane. The Joker and the Red Skull fight atop the bomb, which suddenly drops toward the ocean, carrying the two villains. Cap and Bats manage to steer the plane to safety as the bomb detonates—though the two heroes are certain that is not the end of their archenemies.
Epilogue, twenty years later: Captain America is found frozen in ice, floating in the Atlantic. He is rescued by the next generation of heroes, Batman and Robin, who are now the grownup Dick Grayson and Bruce Wayne, Jr. Returning home, he is welcomed back by the retired Bruce Wayne.