ATRAGON
The story begins as a man realizes that his cab driver is taking him in the wrong direction. Reaching for the driver, the man receives an electrical shock and slumps into his seat, unconscious.
On the waterfront, a sinister gangster fires his pistol. Photographer Susumu Hatanaka snaps a photo and prepares his next shot. Telling his colleague, Yoshito Nishibe, to remove his gangster costume, Susumu gives his bikini-clad female model posing directions. Telling her to look dramatic, Susumu scolds the model for being too intense. The frightened woman points to the pier, where a weird creature is climbing from the water. Susumu snaps pictures of the being, the flash blinding it and causing it to drop back into the sea. At just that moment, the taxi comes screeching past. It does not stop and plunges into the sea, disappearing beneath the water.
The next day the car is dredged from the harbor. No one is inside and divers can find no bodies. Susumu and Yoshito are present as a police inspector questions the real cab driver, who has identified his stolen vehicle. A journalist, Umino, observes the police interrogation. The cab driver states that he was attacked by a man whose hands were as hot as a blowtorch. Susumu and Yoshito back up the story, saying the creature they saw was steaming. The inspector is somewhat dubious about their story.
Susumu sees a beautiful woman disembark from a ship. Deciding that he would like her as a model, he tries to approach her, but the woman enters a waiting car and leaves. Susumu snaps a picture of the departing car. From the shadows, a lurking man also watches the car leave.
In his darkroom, Susumu develops his photographs. He tells Yoshito to try and find the woman, using the license plate on the picture he snapped. At that moment, Susumu's secretary tells him that the police inspector is waiting to see him. There has been another kidnapping, exactly like the one the previous night. Both men were civil engineers, experts in cave-ins. The inspector is not so sure Susumu and Yoshito imagined their steaming creature now. Just then, an earthquake rocks the building.
At the Kokoku Shipping Company, the woman Susumu is looking for, Makoto Shinguji, announces the reporter Umino to her uncle Kosumi. Although Kosumi does not want to see the man, Umino forces his way in. He wants to discuss a mystery from WWII with the man who was once an admiral in the Imperial Japanese Navy. He asks about a missing super submarine - the A-403. Its captain was a man named Shinguji, Kosumi's aide at the time. Umino refutes Kosumi's statement that the A-403 was destroyed off of Saipan and insists that Captain Shinguji is still alive.
Meanwhile, Yoshito reports that he has found the woman to Susumu. Kosumi tells Makoto that her father is dead, the reporter is making up stories. The two leave the building, followed by both Susumu and Yoshito and the reporter Umino. In the car, Makoto tells Kosumi that there is a strange man that has been following her.
Kosumi suddenly realizes that they are taking a different road than usual. He also discovers that the man driving is not his usual driver. The driver coldly demands that Kosumi be quiet. Following behind, Susumu and Yoshito realize that something is wrong. They follow the car to the beach.
The driver stops, forcing Kosumi and Makoto out of the car at gunpoint and leading them toward the sea. Susumu and Yoshito follow the trio, confronting the driver. After a brief scuffle, in which the driver amazingly superheats the metal wrench Yoshito tries to use to club the villain with his bare hand, the two men become prisoners as well. The driver states that he is taking them to the Mu Empire and that he is a Mu agent. Kosumi calls him mad; saying that Mu sank beneath the Pacific thousands of years ago. The Mu agent agrees, claiming his people now live below the ocean floor. Lights appear out at sea, more of the creatures Susumu and Yoshito saw. They are also Mu agents waiting to be retrieved by a submarine. Mu Agent #23 becomes distracted by the submarine's appearance and Susumu attacks him, knocking the gun from his hand. Kosumi grabs the pistol, turning the tables on the Mu agent. The agent escapes, diving into the sea, promising that they will meet again.
Kosumi, Susumu and Yoshito take their story to the police. The inspector is fascinated by their claims. As he listens to their tale of Mu agents and submarines, a package arrives. Inside is a small box with lettering spelling 'Mu'. A film reel rests inside the box. The film shows the Mu Empire, its cavern cities and incredibly vast power generators using the heat of the earth's core. An elaborate temple is shown within which rests the intact A-403, the missing submarine. The film's narrator says that they captured the ship, but not its crew. He claims that Captain Shinguji is designing a powerful new undersea battleship called Atragon. The Mu Empire will once again rise to dominate the surface world. The curse of Mu's god Manda will be on all who oppose them.
The film causes great distress among the officials and military leaders viewing it. The possible threat of Mu is an international one and it is decided to inform the UN. The film is denounced as a hoax and the threat of the Mu Empire is dismissed. Even as the crew of a Japanese ship listens to this news on the radio, strange steaming objects are sighted. More of the objects appear, surrounding the ship. They are mines, released by a submerged Mu submarine. The mines are attracted to the ship and the doomed vessel soon explodes in a great fireball. At once, the threat of the Mu Empire is taken seriously and the world's navies are mobilized.
The U. S. Navy's most powerful submarine, Red Satan, sights a Mu vessel. The commander decides to follow the Mu submarine, hoping to find their base. The Mu sub lures Red Satan ever deeper into the ocean depths. Finally, the mounting water pressure is too great. The Red Satan's hull creaks and groans, preceding the complete implosion of the American submarine.
The destruction of Red Satan alarms Japanese military commanders. Due to the great depth, a nuclear attack against the Mu Empire is impossible. Only Atragon seems to be a weapon capable of dealing with the undersea invaders, as they fear its potential. They try to impress Kosumi to contact Captain Shinguji. Kosumi has no idea where the man is. He kept quiet about Shinguji to hide the truth. Shinguji did not die in the waters off Saipan. He was a deserter. Makoto interrupts, saying that the police wish to see Kosumi. They have captured a Mu agent.
The man in jail is the one who has been following Makoto, but he is not the Mu agent who tried to abduct Kosumi and Makoto on the beach. The prisoner angrily declares that he is not a Mu agent. The inspector says that the only information the man will give is a number. Kosumi understands, it is a serial number, one of the only pieces of information a POW can give. He identifies himself as the former Admiral Kosumi. The prisoner replies by identifying himself as Radio Assistant Totomo Amanoshomi. His commander is Captain Shinguji. Amanoshomi is released, but refuses to say where Captain Shinguji is.
At that moment, an earthquake rocks the building. The voice of Mu Agent #23 comes from the intercom, saying that the quake is no accident. Everyone hurries to the broadcasting room, finding not the agent but a tape recording of his threats. Again, Amanoshomi is pressed to divulge Captain Shinguji's location. Umino interrupts, adding his snide comments about Makoto deserving to see her father to Kosumi's pleas to reveal where Shinguji is. Amano still refuses to tell, but agrees to lead them to his commander. Umino accompanies the group, the police inspector saying that otherwise the reporter would have released the story, ruining the secrecy of the operation.
In the cavernous depths of the Mu Empire, Agent #23 reports to the High Priest of Manda. He reports that the Admiral's party is being followed to Shinguji's location. The High Priest gloats over the blueprints taken from the A-403, saying that soon they will capture Atragon and claim it for the Mu Empire. An earthquake shakes the palace, the result of a cave-in orchestrated by the prisoners enslaved by Mu. The High Priest leads the people of Mu in prayer to Manda, praying for victory and the subjugation of the surface world.
A small boat carries the heroes through a foggy sea. Amano says they will reach the island that is their destination by nightfall. Unobserved, Umino drops a small object over the side of the boat. It is a beacon, guiding a Mu submarine that is following them.
The group lands on the island and is soon confronted by sentries wearing Imperial Japanese uniforms. Amano conducts them through the guards. The group boards a jeep and is driven across the island. During a pause in the journey, Umino notes the island's vast mineral deposits.
Soon, the group reaches a villa built into the side of a cliff. As they wait to see Captain Shinguji, Susumu remarks that he has seen no place in which to build a submarine. Umino replies that the shipyard is underground, claiming he can hear heavy machinery below them. Captain Shinguji then arrives, greeting Kosumi formally, sparring only a brief glance at Makoto. He thanks Kosumi for his silence about his desertion. Kosumi introduces Shinguji to his daughter, who he last saw when she was three. The Captain quickly returns to talking business with his visitors.
His old crew has been augmented, he says, by native islanders. The island has proved an excellent base. He tells Kosumi that he may see Atragon tomorrow when it is tested to determine its completion. He says Atragon was constructed to make Japan invincible. When Kosumi tells him of the Mu Empire and that the entire world needs Atragon, Shinguji angrily declares that Atragon is for the glory and honor of Japan alone. He will not let it be used to protect other nations.
A tearful Makoto suddenly bolts from the room. Susumu angrily challenges Shinguji, berating him for his indifference toward his own daughter. Susumu leaves to find Makoto.
The next day, the visitors discuss Captain Shinguji. A lieutenant leads the group down to the subterranean dockyard, collecting the wayward Umino on the way. A hidden entrance in a rock leads down to the massive complex. The visitors marvel at the enormous ship. Atragon is prepared and Captain Shinguji briefly salutes Admiral Kosumi before boarding Atragon. The ship is moved into a giant airlock which is slowly filled with water. The visitors head back to the surface to await Atragon's appearance.
Kosumi's group waits on the beach. Soon, the water bubbles and churns. The mighty ship breaks the surface, rising into the air via a series of jets, hovering over the lake. That night, Shinguji's command celebrates their success. Tomorrow the Zero cannon will be tested, a weapon which freezes its targets.
At Kosumi's request, Shinguji explains how Mu got the A-403 and the rough design sketches for Atragon. During the closing days of WWII the A-403 was attacked by a submarine of unknown nationality and possessing superior weaponry. He ordered the ship abandoned, the crew barely escaping. Mu must have captured the A-403 and the plans for Atragon. Kosumi again asks that Atragon be used to defend the nations of earth and Shinguji again insists that Atragon is for the glory of Japan alone. Kosumi says Shinguji is betraying the world by his actions, upsetting Shinguji greatly.
Captain Shinguji later talks to Makoto alone on the beach. She says that she hates her father because he refuses to help fight against Mu. Tearfully, Makoto runs off. Shinguji sees Susumu nearby and asks if Susumu also thinks he is a traitor. Susumu says yes. Disgusted, Susumu turns to leave. Shinguji stops him, showing him a picture of his daughter that he has carried for 20 years. He asks Susumu to take care of Makoto.
Makoto heads back to her room, but is stopped by Umino. The spy tells her that he is taking her to Mu, shocking the woman into unconsciousness. Susumu appears and confronts the spy. Umino says he is trying to save Makoto because there is a bomb on the dock. As the distant sound of the explosion is heard, Umino gains the upper hand and subdues Susumu. The saboteur's bomb destroys the drydock. Umino escapes with his two prisoners.
In the lavish palace of the Empress of Mu, the prisoners are presented to the Mu sovereign. The High Priest of Manda asks what should be done with them. Listening to her advisor, the Empress decides that Susumu and Makoto will be given to Manda. Susumu and Makoto are led to the same cell which holds the kidnapped Japanese engineers. Mu Agent #23 tells Susumu that Captain Shinguji must not complete Atragon, otherwise they will be sacrificed to Manda. A gate in the cell's rear wall provides the doomed people a view of the god of Mu, a huge snakelike dragon.
Shinguji's men shift the rubble in the drydock, trying to free Atragon. At the same time, Mu begins its attack on the surface. Positioned on a mountaintop, the Mu forces launch aerial torpedoes of tremendous power, not even sparing fleeing civilians from their attack.
Susumu is thrown back in the cell after being tortured. He displays a pair of sticks he managed to steal, but now thinks they are worthless. The civil engineers tell him that the sticks are nitroglycerine, used by Mu to excavate through the bedrock.
The Mu Empire makes its demands to the world. If Atragon is not destroyed and the nations surrender, Mu will attack New York and Tokyo, to demonstrate their awesome power. A deadline is given for the surrender of the surface world.
In the drydock, Shinguji's men free Atragon from the steel beam that had fallen atop it. The ship itself is in prime condition. Shinguji activates Atragon's drill and burrows his way to the surface. Shinguji asks Kosumi if he should begin the attack against the Mu Empire. He finally sees that his position was wrong. Atragon will destroy the invaders and protect not just Japan but the whole world.
Tokyo is evacuated as the Mu Empire's deadline approaches. As the JSDF awaits the attack, no Mu forces appear. As the deadline is reached, a horrible earthquake strikes the city, causing much of Tokyo to crumble and sink into the earth. In the harbor, Mu submarines blast ships with heat rays, causing them to explode. The High Priest of Manda gloats at the destruction. Atragon's appearance changes his tune and the High Priest's submarine dives, beating a hasty retreat. Atragon plunges from the sky, intent on pursuing the Mu vessel back to its base.
The Empress of Mu visits her prisoners to conduct them to Manda. Susumu seizes her, holding her hostage with the nitro. The Empress' entourage is locked in the cell, while the surface dwellers escape, taking the Empress with them as a hostage. They reach an air lock, overcoming the sentries. As Susumu examines the pressure-resistant diving suits inside the airlock, no one observes the Empress subtly press a button. The side of an undersea cliff crumbles away and Manda is freed. Susumu forces the Empress to also don a diving suit, letting in some water when she refuses.
The Mu submarine returns to Mu, with Atragon in pursuit. At the same time, the surface prisoners try to escape from the air lock, but their path is blocked by Manda. Shinguji sees both the monster and the people menaced by Manda. He orders Atragon's diving hatch lowered for the escapees. Dye-filled torpedoes produce an inky cloud which blinds Manda and allows the escapees to swim to Atragon. With the prisoners onboard, Atragon surfaces.
Makoto is joyfully reunited with her father, proud that he has finally decided to help. Captain Shinguji tells the Empress to call of her attack. When she refuses, Shinguji decides he will use Atragon to destroy the Mu Empire's power source. The undersea battleship returns to the deep.
Manda sees Atragon and attacks, wrapping his snakelike body around the ship and trying to crush it. Shinguji orders an electrical current sent through the hull, shocking Manda and making him break off the attack. Atragon pursues the dragon, using the Zero Cannon to freeze Manda against the face of an undersea cliff. Atragon then begins to burrow its way toward the Mu power source. The ship breaks into the power room and a strike force disembarks to destroy the power source. The Mu soldiers are unable to fight against the freeze guns of the commandos from Atragon and the power source is soon reached. A powerful explosive is set against the machinery and the strike force retreats back to Atragon. The ship uses the Zero Cannon to freeze part of the Mu power generator before withdrawing back into the tunnel the ship has burrowed.
Atragon resurfaces. Far below, the bomb goes off, the massive explosion reacting with the Mu Empire's powerhouse. An enormous fireball explodes from beneath the sea. Some fleeing Mu submarines attempt to engage Atragon, but the Zero Cannon soon freezes them solid and they are destroyed by the expanding explosion.
The Empress of Mu breaks away from her guards. Captain Shinguji orders the men to let her go. The Empress wishes to share her nation's fate. The Empress dives over the side of Atragon and swims into the explosion which has claimed her empire.
