Pilot David Randall is paid to fly top-secret photographs from South African astronomer Dr. Emery Bronson to Dr. Cole Hendron in the United States. Hendron, with the assistance of his daughter Joyce, confirms their worst fears: Bronson has discovered a rogue star named Bellus that is on a collision course with Earth.
Author and amateur astronomer John Putnam (Richard Carlson) and schoolteacher Ellen Fields (Barbara Rush) watch a large meteorite crash near the small town of Sand Rock, Arizona. At the crash site, Putnam notices a strange, partially buried object lodged in the large crater; he comes to the realization that it wasn't a meteorite that crashed but a large alien spaceship. After a landslide completely covers the mysterious spacecraft, his story is later scoffed at by the townspeople of Sand Rock, including its sheriff (Charles Drake), and the local media.
Lou Francis (Lou Costello) and Bud Alexander (Bud Abbott) have just graduated from a private detective school. Tommy Nelson (Arthur Franz), a middleweight boxer, comes to them with their first case. Tommy recently escaped from jail after being accused of murdering his manager, and asks the duo to accompany him on a visit to his fiancée, Helen Gray (Nancy Guild). He wants her uncle, Dr. Philip Gray (Gavin Muir), to inject him with a special serum he has developed which will render Tommy invisible, and hopes to use the newfound invisibility to investigate his manager's murder and prove his innocence. Dr. Gray adamantly refuses, arguing that the serum is still unstable, recalling that the formula's discoverer John Griffin was driven insane by the formula and did not become visible again until after he was killed. However, as the police arrive Tommy injects himself with it and successfully becomes invisible. Detective Roberts (William Frawley) questions Dr. Gray and Helen while Bud and Lou search for Tommy.
Scott Carey (Grant Williams) is a businessman who is on vacation with his wife Louise (Randy Stuart) on a boat off the California coast. When Louise goes below deck momentarily, a large, strange cloud on the horizon passes over the craft, leaving a reflective mist on Scott's bare skin. Louise is slightly alarmed when she comes above deck, and the two are puzzled by the phenomenon that disappears as quickly as it had it shown up.
A group of 30 scientists travel from Earth to a nearly-identical alien planet that is culturally and technologically centuries behind. The inhabitants of this planet have brutally suppressed a renaissance movement, murdering anybody they consider to be an intellectual, and thus the planet is stuck in the middle ages. Anton, one of the scientists from Earth, is sent to infiltrate the local populace of the Kingdom of Arkanar and help them progress as a society, although he is forbidden from getting involved with local politics or forcibly interfering with the advancement of technology or culture. He assumes the identity of Don Rumata, a nobleman who resides in a large castle surrounded by poverty. There, he lives with Ari, a young woman who he has taken as his bride, and the juvenile prince of Arkanar. Rumata's presence divides local opinion; some treat him as a God, others despise him.
Scientist Dr. Russell Marvin (Hugh Marlowe) and his new bride Carol (Joan Taylor) are driving to work when a flying saucer appears overhead. Without proof of the encounter, other than a tape recording of the ship's sound, Dr. Marvin is hesitant to notify his superiors. He is in charge of Project Skyhook, an American space program that has already launched 10 research satellites into orbit. General Hanley (Morris Ankrum), Carol's father, informs Marvin that many of the satellites have since fallen back to Earth. Marvin admits that he has lost contact with all of them and privately suspects alien involvement. The Marvins then witness the 11th falling from the sky shortly after launch.
On a volcanic island near the kingdom of Hetvia rules Count Dakkar, a benevolent leader and scientist who has eliminated class distinction among the island's inhabitants. Dakkar, his daughter Sonia and her fiance, engineer Nicolai Roget have designed a submarine which Roget pilots on its initial voyage just before the island is overrun by Baron Falon, despotic ruler of Hetvia. Falon sets out after Roget in a second submarine and the two craft, diving to the ocean's floor, discover a strange land populated by dragons, giant squid and an eerie undiscovered humanoid race.
African-American coal mine inspector Ralph Burton (Harry Belafonte) becomes trapped underground in a cave-in while inspecting a mine in Pennsylvania. He can hear rescuers digging towards him, but after a few days they slow down and then stop completely. Alarmed, he digs his own way out. Reaching the surface, he finds a deserted world. (No bodies are seen at any time in the film.) Some discarded newspapers provide an explanation: one proclaims "UN Retaliates For Use Of Atomic Poison", another that "Millions Flee From Cities! End Of The World". Ralph later plays tapes at a radio station that an unknown nation had used radioactive isotopes as a weapon, yielding a dust cloud that spread globally and was completely lethal for a five-day period.
The grandson of Dr. Jack Griffin, the original invisible man, has emigrated to the United States and now runs a print shop in Manhattan under the assumed name of Frank Raymond (Jon Hall). In his shop he is confronted by four armed men who reveal that they know his true identity. One of the men, Conrad Stauffer (Cedric Hardwicke), is a lieutenant general of the S.S., while a second, Baron Ikito (Peter Lorre), is Japanese. They offer to pay for the invisibility formula and threaten amputation if it is not revealed. Griffin manages to escape with the formula in his hands.
Six children are identified by a team of UNESCO researchers investigating child development. The children have extraordinary powers of intellect and are all able to complete a difficult brick puzzle in exactly the same amount of time.
Phileas Fogg III (Jay Sheffield), great-grandson of the original Phileas Fogg, accepts a bet to duplicate his great-grandfather's famous trip around the world in response to a challenge made by Randolph Stuart III, the descendant of the original Fogg's nemesis. Unbeknownst to anyone, however, "Stuart" is the infamous con man Vicker Cavendish (Peter Forster) who made the bet in order to cover up his robbing the bank of England by framing Fogg for the crime.
Mankind has achieved space flight capability and built "The Wheel" space station in orbit 1,075 miles above Earth. It is commanded by its designer, Colonel Samuel T. Merritt (Walter Brooke). His son, Captain Barney (Eric Fleming), having been aboard for a year, wants to return to Earth.
The film reduced Wells' tale to an "Ecology Strikes Back" scenario, common in science fiction movies at the time. The "food" mysteriously bubbles up from the ground on a remote island somewhere in British Columbia. Mr. and Mrs. Skinner (John McLiam and Ida Lupino) consider it a gift from God, and feed it to their chickens, which grow larger than humans as a result. Rats, wasps, and grub worms also consume the substance, and the island becomes infested with giant vermin. One night, a swarm of giant rats kill Mr. Skinner after his car breaks down in the forest.
In the near future, a revolutionary new psychotherapy treatment called dream therapy has been invented. A device called the "DC Mini" allows the user to view people's dreams. The head of the team working on this treatment, Doctor Atsuko Chiba, begins using the machine illegally to help psychiatric patients outside the research facility, using her alter-ego "Paprika", a sentient persona that she assumes in the dream world.
Through her stepsister Claire Clairmont (Miriam Cyr), Mary Godwin (Natasha Richardson) and her future husband Percy Shelley (Julian Sands) came to know Lord Byron (Gabriel Byrne). During the summer of 1816, Lord Byron invited them to stay for a while at Villa Diodati in Switzerland. There they met Byron's physician friend, Dr. John Polidori (Timothy Spall). On June 16th, while a storm raged outside, the five of them amused themselves by telling ghost stories and revealing private skeletons. From Mary's previous experience of miscarriage came the desire to raise her child from the dead, which led to the creation of the Frankenstein monster. From Polidori's homosexuality, suicidal thoughts, and fascination with vampires came the story "The Vampyre".