U.S. Navy sailors and childhood friends, David Herdeg and Jim Parker, are stationed in Philadelphia, Pennsylvania, during 1943. As part of a top-secret military experiment, they report for duty on the destroyer USS Eldridge where they are in charge of special generators developed by scientist Dr. James Longstreet to deflect radar. As the destroyer sails into Philadelphia harbor, Longstreet monitors the test from an aircraft carrier docked at base and gives instructions to activate the generators, then power up the energy field. The officers on the aircraft carrier are amazed as the Eldridge disappears from radar, a breakthrough that will give the Americans a distinct advantage in the war. However, an unintended consequence occurs when the destroyer vanishes. A panicked Longstreet orders the Eldridge to shut down the generators, but there is no communication with the destroyer. Meanwhile, David and Jim flee from the special equipment room when the generators appear on the verge of exploding. As a strange energy field pervades the destroyer and its crew, David and Jim jump overboard. However, instead of falling into water, they spin through a time-travel vortex. The two sailors land in a small, uninhabited Nevada town at night and immediately pursued by gunfire from a helicopter. They run toward a security fence, which sparks and catches fire when David and Jim touch it. The resulting explosion destroys the helicopter, while the two sailors escape unharmed. At sunrise, they find themselves in a desert. Jim speculates they are hallucinating as part of the experiment, but David believes a serious malfunction has occurred. Meanwhile, the elderly Dr. James Longstreet inspects the desert area after conducting a radar deflection experiment similar to one in 1943. Longstreet’s assistant, Barney, is shocked that their test subject, the uninhabited Nevada town, has inexplicably disappeared. Longstreet observes a metal pole on the ground, which was not previously there. Back at his office, the scientist identifies the pole as the mast of the Eldridge. Arriving at a roadside diner, David and Jim stare at a television and look around in amazement at how people are dressed. David attempts to telephone the Philadelphia Naval Base, but no one recognizes the name of his commander. Outside, a lightning storm is on the horizon, and Jim experiences a painful throbbing in his hands. He backs into the diner’s video game machines, causing them to spark and malfunction. Demanding that Jim pay for the machines, the owner of the diner aims a gun, but David quickly confiscates the weapon and commandeers a car belonging to Allison Hayes. Since David is not familiar with automatic transmission, he orders Allison to drive. She is further baffled when the two strangers appear ignorant that the year is 1984 and that the U.S. won World War II. Meanwhile, Dr. Longstreet and his colleagues try to understand why the town has failed to rematerialize, and they track the unusual lightning storms in the area. Major Clark reports to Longstreet that he is looking for two unknown men, who breached security at the town test site. Along the highway, local police apprehend David and Jim for kidnapping, but Allison does not believe her abductors are criminals and refuses to press charges. Jim’s condition worsens, and he is hospitalized with severe seizures. Although reluctant to talk at first, David is worried about his friend and explains to attending physician, Dr. Magnussen, that he and Jim participated in a classified military experiment involving radar deflection. When David says they were somehow moved across time from 1943, the doctor appears skeptical. Magnussen and David are both dumbfounded when Jim is overcome by seizures and disappears in a flurry of electrical sparks. David flees the hospital as military police arrive and, once again, relies on a trusting Allison to help him escape. Together, they drive to David and Jim’s hometown, Santa Paula, California. Storms continue to gather around the test site of the disappeared town, and Dr. Longstreet informs Barney that the experiment inadvertently opened up a vortex that is pulling air toward it, like a vacuum. The military sends a missile probe into the hole, and the video reveals that the Eldridge is stuck in the vortex, along with the Nevada town. Dr. Longstreet interviews Dr. Magnussen, who identifies David Herdeg and Jim Parker from a 1943 photograph, confirming Longstreet’s suspicions that his 1943 experiment has somehow collided with this one in 1984. As the vortex grows, Barney estimates it will endanger the entire planet. In Santa Paula, David and Allison arrive at a ranch, which still belongs to Jim Parker’s family, and greet Jim’s wife, Pamela Parker. Now in her sixties, Pamela stares in amazement at the young David she knew in 1943, and suddenly realizes that her husband was telling the truth all these years about time travel, but everyone considered him deranged. She reveals that Jim survived the Philadelphia experiment in 1943 and is still alive, while other sailors on the Eldridge were burned or died. However, David never came back. David walks outside to say hello to Jim, but the old man is unable to face the trauma again and shuns his friend. As Allison and David leave, military police pursue them. When one of the police vehicles crashes, David finds documents inside the car naming Dr. Longstreet as the person in charge of the Nevada town experiment. David and Allison hitch a ride and return to Nevada to find Longstreet. Along the way, Allison reveals her feelings for David, and the two kiss. As they get closer to the vortex, David begins to experience the same painful symptoms that affected Jim. At Longstreet’s home, David abducts one of the scientist’s colleagues at gunpoint and forces him to take them to the secured military base where Longstreet is working. David charges onto the base, as storms batter the facility. In the control room, he confronts Longstreet, and the scientist shows him video of the Eldridge and the Nevada town trapped in the vortex. Longstreet explains that the electro-magnetic fields of the 1943 and 1984 experiments must have cross-connected to create a hole in the space-time continuum, and David fell through it. Longstreet tells David he must return to the destroyer in order to close the vortex. According to interviews conducted with the Eldridge sailors in 1943, the ship reappeared after David shut down the generators. Before returning, David says an emotional goodbye to Allison. Wearing an astronaut-like suit, he is positioned directly under the vortex and sucked into the whirling black hole. David lands back on the destroyer and uses an axe to destroy the generator, allowing the Eldridge, its crew, and Jim to reappear in 1943. Instead of remaining in 1943, David jumps overboard once again. After the control room video confirms that David successfully closed the vortex, Allison drives to the Nevada town, which has also rematerialized, and finds David waiting for her.