Doctor Howard Latimer answers what he believes to be a request for a favour from an American friend by picking up a famous German actress from London Airport. He goes in the company of a journalist Geoffrey Windsor who tags along after failing to gain an interview with Latimer about recent medical research. As Latimer is already late for a date with his fiancee at the Royal Festival Hall he lets Windsor take the actress to Claridges Hotel.
During the closing days of the Second World War, six members of his Royal Canadian Air Force fighter squadron are killed due to a command decision made by pilot Ted Stryker (Dana Andrews). Years later, in civilian life in Ottawa, Ontario, Canada, a guilt-stricken Stryker goes through many jobs, and his marriage is in trouble.
In the Arizona Territory of the 1880s, rancher Dan Evans (Van Heflin) and his young sons witness a stagecoach holdup. The boys want to try to intervene, but their father warns them that it would be useless to act when they are so heavily outnumbered. When the stagecoach driver overpowers one of the robbers and uses him as a human shield, Ben Wade (Glenn Ford), the leader of the gang, callously shoots both men dead.
Carl Schaffner (Steiger) is a crooked English (previously German) businessman who flees to Mexico after stealing company funds. While travelling by train, Schaffner decides to evade authorities. He drugs and switches identities with fellow train passenger Paul Scarff, who looks like him and has a Mexican passport. He throws Paul Scarff off the train, injuring Scarff. Carl later discovers that Scarff is wanted in Mexico as a political assassin. Carl then tracks down Scarff, who is resting from his injuries, to get back his original passport. Carl arrives in Mexico and is captured by the local police, who mistake him for Scarff. Carl then fights to show his true identity to the local police. The plan seems foolproof until he is forced to care for the dog of Scarff. The local police chief and Scotland Yard inspector Hadden conspire to keep him trapped in the Mexican border town of Katrina in an effort to get him to cross the bridge back into the U.S. and face justice. The misanthropic Schaffner has grown attached to Scarff's pet spaniel and is tricked into going across the dividing line of the bridge to get the dog. He is accidentally killed trying to escape the authorities. The final irony is that the discovery of his own humanity has cost the cynical, friendless Schaffner his life.
An early morning test explosion of the first atomic plutonium bomb is planned at a military site in Desert Rock, Nevada. When the chain reaction for the charge fails its cycle and does not detonate as expected, Lt. Col. Glenn Manning (Glenn Langan) receives orders to keep his men in the protective trench, as an explosion is still imminent, but its timing is now unknown. Moments later, an unidentified small civilian aircraft crash-lands near the bomb site, and Glenn leaps from the trench and runs into the detonation area to rescue the pilot. Once in the detonation area, the bomb goes off, and Glenn is caught in an atomic blast that burns him and immediately disintegrates his clothes and hair.
Eddie Rico (Richard Conte) is the owner of a prosperous laundry company in Bayshore, Florida who was the former accountant for a major crime syndicate years ago. He has given up his ties to the syndicate, and hopes to adopt a child with his wife, Alice. When Eddie receives a call asking to give a job to Wesson (William Phipps), a junior mobster, and Alice becomes worried that the syndicate will attempt to bring Eddie back into a life of crime. Eddie calms her down, but then he receives a letter from his mother saying that his two brothers, Johnny (James Darren) and Gino (Paul Picerni), have disappeared. On the way to work, Gino finds Eddie and asks for his help in leaving the country: Gino admits to being the gunman for a gang killing and Johnny was the driver. Gino now believes the syndicate is after him, and he was ordered to St. Louis later that day. Eddie, who does not believe that the syndicate is after them, tells Gino to go to St. Louis and gives him some money. When Eddie returns to work, he finds out that the syndicate boss, "Uncle" Sid Kubik (Larry Gates), has ordered him to Miami. Eddie leaves despite his wife's objections that he will miss an adoption interview.
Professional burglar Nat Harbin (Dan Duryea) and his two associates, Baylock (Peter Capell) and Dohmer (Mickey Shaughnessy), set their sights on wealthy spiritualist Sister Sarah (Phoebe Mackay), who has inherited a fortune — including a renowned emerald necklace — from a Philadelphia financier. Using Nat's female ward, Gladden (Jayne Mansfield), to pose as an admirer and case the mansion where the woman lives, they set up what looks like a perfect break-in; even when Nat's car is spotted by a couple of cops, he bluffs his way through, gets the necklace, and makes the getaway. But the trio—plus Gladden—can't agree on how to dispose of the necklace, and soon their bickering becomes a lot less important than the fact that someone is on to what they've done—a woman (Martha Vickers) is working on Nat, while a man (Stewart Bradley) is working on Gladden. Equally serious, the trio kills a New Jersey state trooper while on their way to warn her. And among the cops chasing them is one with larceny in his heart and murder on his mind.
The American Buckley-class destroyer escort USS Haynes detects and attacks a German U-boat that is on its way to rendezvous with a German merchant raider in the South Atlantic Ocean. Captain Murrell (Robert Mitchum), a former officer in the merchant marine now an active duty lieutenant commander in the Naval Reserve, has recently taken command of the Haynes, even though he is still recovering from injuries incurred in the sinking of his previous ship. Before the U-boat is first spotted, one sailor questions the new captain's fitness and ability. However, as the battle begins, Murrell shows himself to be a match for wily U-boat Kapitän von Stolberg (Curt Jürgens) (portrayed as not being enamoured with the Nazi regime) in a prolonged and deadly battle of wits that tests both men and their crews. Each man grows to respect his opponent.
In Moscow, four terrified women prisoners are brought to the office of Joseph Stalin, who chooses Dasha, the smallest and most beautiful, and punishes her by shaving off her long hair. Moments later, plastic surgeon Dr. Petrov leads Stalin into the operating room and transforms his face so that he is unrecognizable. After his handlers announce publicly that Stalin has died, they secret him away to a hideout, where Greta Grisenko serves as his nurse. Meanwhile, Greta's twin sister Lili continues searching for her, as she has been ever since Russian troops invaded their home country of Lithuania and took Greta, against her will, to Moscow. Earlier, Lili had engaged private investigator Steve Anderson, an American living in Berlin, to find Greta, and now locates him there and asks why he has failed to contact her with information about her sister. Steve has discovered that Greta is working in Moscow and, despising Communists, refuses to work with Lili until she convinces him that her sister is an innocent victim of the Russians.
Tom Yately, just released from prison, is determined to start a new life and he gets a job as a driver at Hawletts, a haulage company that transports loads of ballast gravel from a nearby quarry. The truck-drivers are offered bonuses by the agent Cartley for delivering their loads at dangerously high speeds along narrow roads. Tom is accepted by the other drivers except Red, the foreman and head driver and also a violent bully. Tom soon becomes friends with Gino, an Italian driver who is in love with Cartley's secretary Lucy. Red offers a cash bonus to any driver who can make more runs than him and Tom is determined to try.
On a dark night, Jōji (Yujiro Ishihara) an ex-boxer, meets Saeko (Mie Kitahara), a club singer on the verge of suicide. They live and work together at a restaurant where they begin to fall in love, struggling to escape from their dark pasts. Jōji deals with his failure as a boxer, shamed of having been barred from the ring. Saeko hopes to hide from gangsters who have forced her to work at their cabaret. She seeks his help as she is trying to run away from her gangster boss who is forcing her to continue working even though she no longer has a talented voice due to illnesses.
In England, Professor Harrington (Maurice Denham) visits his rival, Dr. Julian Karswell (Niall MacGinnis). Harrington promises to cancel an investigation of Karswell's involvement in Satanism if Karswell will rescind a threat he has made against Harrington. After learning that a parchment given to Harrington has disintegrated, Karswell glances at the clock and ushers Harrington out, promising to do all that he can. As Harrington drives home, a gigantic demon materialises in the woods and pursues him. Losing control of the car, Harrington crashes into an electrical pole and is electrocuted by falling high tension lines.
Michael Cannon (Richard Burton) returns to London after the Second World War and places advertisements in the personal column of various newspapers (The Daily Telegraph distributed miniaturised copies of the newspaper showing the 'ad' at U.K. cinemas after each performance of the film), in which "Biscuit" tries to get in touch with "Sea Wife". Eventually Cannon, who is Biscuit, receives a letter summoning him to the Ely Retreat and Mental Home. There he meets an ill man nicknamed "Bulldog" (Basil Sydney). Bulldog tries to persuade Biscuit to give up the search. A flashback reveals the backstory.