We open with a long shot of a rocket awaiting launch. Captain Neal Patterson (Eric Fleming), Lt. Mike Cruze (Dave Willock) and Lt. Larry Turner (Patrick Waltz) wait outside the Colonel's office. When admitted they are introduced to Professor Konrad (Paul Birch) and told their next assignment is to take Konrad to the Space Station. They express disappointment at such an unimportant assignment, but Col. Ramsey (an uncredited Guy Prescott) cryptically tells them, "There are indications of serious trouble up there. Professor Konrad will tell you about it when you're underway."The crew prepares for launch when Konrad arrives. He explains the importance of the Space Station as a launching point for all future space missions. Outside, Larry is saying goodbye to his girlfriend (an uncredited Joi Lansing). With Larry back on board, Prof. Konrad is strapped into his bed for launch. The crew grimaces with the G-forces of acceleration until they reach orbit. They navigate towards the Space Station. Konrad tells Patterson about the true nature of the mission, "They've made some disturbing observations from the Space Station. Apparently we have some deadly neighbors in outer space. The Earth may be in mortal danger." At that a ray of energy from an unknown origin flashes across the screen. Multiple shots get closer to the Space Station until one makes a glancing blow. The next shot is a direct hit and the wheel-shaped craft is destroyed. The beams are approaching the spaceship, Starfire. They try to outrun the energy force and are struck. The force accelerates the craft to an incredible speed. Later they will discover the speedometer broken above the maximum pegged value. Capt. Patterson was injured by a piece of flying debris.Title and credits roll [15 minutes into the movie] over a star field. They approach a planet and crash land in the snow. The crew awakens to take stock of their situation. They deduce they are on the planet Venus and discover the air is breathable. Below the snowline they enter a jungle with strange plants and no sound at all. A strange pulsating sound pierces the silence and Prof. Konrad correctly observes, "My guess is that was an electronic signal of some kind." They build a camp fire and bed down for the night. Larry takes the first watch. Mike took the watch that brought morning, but he dozed off. As a result, he didn't notice until too late the crew were surrounded by the inhabitants of the area. Women in short shirts, clear plastic high-heel shoes, and carrying ray guns take them hostage. They are marched back to the city. Once inside the city they get the impression that strangers, and particularly male strangers are not welcomed. They are brought into the Council Chamber for an audience with the rulers of Venus.A curtain parts and Queen Yllana (Laurie Mitchell) and her council, all wearing masks, take their seats at a table on a raised platform. Yllana introduces herself, "I am Yllana, ruler of the city of Kadir and queen of this world." Next she asks, "Why are you here?" Patterson introduces himself and his colleagues, then explains, "We came from Earth on a peaceful mission, but our ship was thrown off course, and we crashed here." The Queen does not believe the Earthmen. She and her council adjourn to decide their fate. Motiya (Lisa Davis), the blond woman that Larry found so captivating, leaves to tell Talleah (Zsa Zsa Gabor) of the Earthmen. Talleah, the leader of the resistance movement on Venus, decides to visit the Earthmen and decide for herself if they can be trusted to help her cause. The Earthmen are returned to the Council Chamber to hear the decision. The Queen pronounces that, "You came here to spy on us, to prepare for invasion. What is the plan of attack? You will die!" They are returned to the prison quarters.Konrad voices his concern, "I have a sense of foreboding about them. A feeling of something monstrous, evil." Patterson adds, "I'm beginning to think our being here isn't an accident." He concludes the energy beam originated on Venus. Talleah visits the Earthmen. She tells them their lives are in great danger. She confides that she is one of many who want to overthrow the Queen and makes a deal, "If you help us, we are going to help you." Then she drops the bombshell, "The Earth is going to be destroyed." Talleah tells of an interplanetary war Venus had ten years earlier with Mordo. Most of the cities were destroyed and lost to the jungle. Yllana led the revolt and took over from the men. Many were killed, but the men she needed are kept on a prison colony moon, Tyrus, that orbits Venus.An escort detail comes to take Capt. Patterson to see the Queen. Konrad noticed the Queen had an interest in Patterson and advises he try to charm her. Betraying her true feeling for Patterson, a jealous Talleah says, "I hate her! I hate that Queen!" Yllana joins Patterson in her bed chamber. She tells him, "Bring me a glass of wine, Captain, and one for yourself." She sits, provocatively on the edge of the bed, showing a lot of leg. They drink. The charm appears initially to be working until she warns, "If you do not give us a truthful explanation of your visit here, the Council sentence will be carried out to the letter." She does provide an escape provision for the handsome Captain. She admits to a desire for him. He asks her to take off her mask, but she refuses. By way of warning, she shows him preparations of the Beta Disintegrator that will be used to destroy the Earth. In a moment of weakness she allows Patterson to unmask her. He is shocked by the visage. Severe radiation burns have left the angry Queen with a scarred face of blue and black skin, with open red sores. "For that you will die," she proclaims. Yllana replaces her mask and calls her guards to escort Patterson back to his cell. When alone, she removes her mask, looks at her face in the mirror and sobs uncontrollably. Patterson explains to his colleagues, "It was atomic radiation that disfigured her. I think its affected her mind." The four are taken to see Talleah in her lab. She introduces another of her circle, Kaeel (Barbara Darrow). Talleah tells Patterson they have no time to waste. She has learned that the Queen plans to destroy the Earth in two days. They plan to walk through the jungle to the site of the Beta Disintegrator and destroy it. Before they can leave, the guards search the lab. Since Talleah is still considered loyal she continues to work as the others hide. When the guards leave, Talleah frees her comrades and the Earthmen and they make their way through the city and escape outside.Odeena (Marilyn Buferd), who brought the Earthmen to see Talleah, has been captured and brought before the Queen. She protests her innocence, and is lulled into a sense of safety when the Queen reassures her, "Odeena has always been loyal to her queen. Release her. You may go." As she turns to leave, Yllana pulls a ray gun from a guard and blasts her into smoke. Outside the city, Talleah, Patterson and the others are under radar and searchlight detection. They conclude they are safest in a cave. The guards are searching in the jungle for them. Larry leaves the safety of the group to explore the cave system. Larry is observed by something that watches from a rock ledge above him. A giant red-eyed spider pounces down on him. He screams and fights it off. The commotion draws the rest to his aid. A blast with a ray gun soon reduces the spider to a smoldering shadow on the ground. They build a fire and wait in the cave. Patterson, Larry and Mike get to know their female companions on a more intimate basis. Konrad remains unattached, so he volunteers to go gather more wood for the fire. Outside he discovers the search party of guards have found their trail and are closing in fast. They devise a plan to have Talleah pretend to capture and march them back to the city.The Queen oversees final preparations on her Beta Disintegrator. She returns to the city to confront the Earthmen, unaware Talleah is no longer loyal. But Talleah reveals herself, "I don't want your reward. One move and I kill you." Patterson orders Yllana to give orders to suspend all work on the Beta Disintegrator. Talleah adds an order of her own, "You will contact the guards on Tyrus and tell them to free all the men." Yllana pretends to comply, goes to her bed and pulls a ray gun out from under a pillow, but is quickly disarmed. Patterson pulls her mask off and gives it to Talleah to masquerade as the Queen to give the orders. They tie up the Queen and hide her behind a screen. Motiya and Kaeel leave to warn their partisans at the weapon site. The masked guards enter the Queen's chamber. Talleah orders them out, but Yllana kicks over the screen revealing the plot. Talleah is disarmed and unmasked. The Queen is restored to power. Yllana delays the execution of the traitors until after she destroys the Earth, but promises, "For her treachery, Talleah will die last, and most horribly of all." Yllana makes one more appeal to Patterson for his love and attention, but her disfigured face even repells her guards.The Earthmen are taken to the jungle site of the weapon. While Yllana gloats, Motiya and Kaeel signal their mission is completed. On a giant screen the Earth is seen suspended in space. The Queen threatens, "It took untold millions of years to create the planet you call Earth. Watch it closely Earthmen. It will be destroyed in a matter of seconds. Watch it!" Yllana presses the button to start the machine. It whirrs up to speed, then makes an unexpected sound of distress. The Queen presses the button again, but all that happens is a screeching sound. She pounds on the button but still nothing happens. The machine explodes and a small fire erupts inside. The Queen enters the main operating room to work it manually. Every lever she throws only makes things worse. More explosions and more fires. A fight between the loyalists and resistance breaks out. A final fireworks display reduces the Queen to a burnt out carcass.Sometime later the Earthmen and citizens of the city assemble in the Council Chambers. A new Queen, Talleah, and her court assume their places on the dais. Talleah announces that the ship has been repaired and the Earthmen can now leave for home. They prepare to depart, but are delayed by a message for the Queen, "The electronic tele-viewer is working. Earth answers us." Colonel Ramsey tells the crew that their orders are, "Not to attempt a return flight in the Starfire. I will not risk his life or the lives of his men in a patched-up ship. Therefore, Captain, you and your crew will remain on the planet Venus until a relief expedition can reach you." We close with Patterson and Talleah embracing, then each principle cast member gets a credit and close-up.