An opening narration talks about the race for the atomic bomb, and countrys endeavors to build ever bigger and more powerful devices. Sometimes doing this leads to accidents and even death.
Scene cuts to a newspaper headline announcing that Dr Karol Noymann (John Caradine) has been killed in an atomic lab explosion. It is noted that the area around the lab is so contaminated by radiation a full investigation has not begun.
The Pentagon takes an intense interest in the accident. Dr Adam Penner (Phillip Tonge) discusses the situation with General Stone (Paul Langton)l. He wants a stop to military application of atomic energy. He wants everything to be on a peaceful basis. Because of the accident to Noymann he has decided to resign.
At Noymanns funeral a strange creature moves around in the background, it briefly becomes visible before once again fading from view
That night Phyllis Penner (Jean Byron) discusses the resignation of her father with John Lamont (Robert Hutton) later in the evening the strange creature visits Noymanns grave and disturbs it
Close to midnight there is a knock at the Penners door. Noymann, corpse, now inhabited by an alien warns Earth has 24 hours to surrender or the aliens will attack and destroy man. He explains the aliens have invisibility technology and 20,000 years ago they aliens invaded the Moon destroying all life on it
Up till now the aliens had little interest in the humans, but with growing technology humans have become a threat, one the aliens plan to nullify. Noymann then hands Penner an invisible piece of metal to demonstrate their science. Man wont be able to fight off the invasion because the aliens ships are invisible. Before leaving Noymann instructs Penner to take this message to the world
Penners daughter and John arrive back at the house and encounter a shaken Penner. John believes his story and sends a message to Washington. We see the result of this communication in a series of newspaper headlines claiming Penner is a mentally unstable old fool.
To try and gather more evidence, John, the professor and his daughter visit Noymanns grave site. All three are stunned to see foot prints appear and move towards the grave. When the movement stops they hear Noymanns voice, he warns Earth will get one more warning then the attacks will begin.
Losing patients the aliens force a plane to crash then re-animate the corpse, who then interrupts a radio broadcast of a hockey match and restates the aliens plan. The process is repeated with a car crash victim, this time broadcasting his announcement at a football game.
The nations of Earth refuses to surrender, in response the aliens re-animate ever increasing numbers of the dead. Soon widespread destruction and panic breaks out around the world. Desperate for a solution the US government announces that Penner and other top scientists are to be taken to hidden locations to work on developing a successful defense against the aliens
Major Bruce Jay (John Agar) is tasked with getting Penner, his daughter and Dr Lamont to one of these locations. On the way they are ambushed by a gunman who orders them out of the car. As the standoff continues the gunman becomes distracted by the noise.
Seeing his chance Jay kills him, but shortly after the corpse is reanimates and begins to follow the jeep trying to find the location of the secret research facility
The group arrives at secret location number 6 without further incident. Making contact with Washington they are apprised of the current situation; things are getting dramatically worse. As they speak to Washington one of the radiation alarms triggers, checking the perimeter monitoring system the deduce an alien ship has landed nearby and is bringing large numbers of the dead back to life in preparation for an attack on the base
That night Washington reestablishes contact with scientists and tells them of a line of research that seems to indicate the technology the aliens are using creates an inherent instability in any material subject to the invisibility process.
Armed with this information Penner quickly makes a break through, he believes they use a ray to mask themselves and if paint preferably acrylic was applied to the corpse it would render them visible and unable to escape.
Jay goes outside to test a new spray device. He finds a suitably possessed corpse and attacks. Initially the attack goes well, but the corpse regroups and Jay fails to capture it.
Back at the base Jay realizes the idea works; he just needs to deploy the paint faster. After modifying the device Jay tries again with the aid of Lamont. The number of corpses has been increasing dramatically and Jay is convinced they must be almost on top of an alien ship. The new plan calls for them to dig a pit filled with the acrylic paint then lure one of the corpses into it. The pair quickly isolate a potential victim and lead him into the trap. As soon as it is covered with the paint it becomes harmless and inanimate.
They take the corpse back to the facility, chased by a number of corpses. Once safe they prepare a pressure chamber and see if that drives the creature out of the body. Their plan works and a ghostly apparition of a humanoid reptile emerges from the body.
Outside the attacks by the corpses intensifies. Cracking under the combined pressure of urgency and fear, Lamont cracks and goes on a rampage causing an electrical surge to run through the buildings equipment triggering a series of alarms.
Penner notices the alien reacts badly to the alarm, and realizes the creatures have a weakness to sound. Penner quickly produces a sound gun and tests it on the alien. At first little seems to happen, then as the frequency changes the creature becomes visible, leaves the corpse and dies.
The team tries to contact Washington but the nearby alien ship jams the signal. Everyone realizes they need to destroy that ship to get the message through.
They rig the gun onto the back of a truck and go looking for the ship using the jamming signal as a marker. Jay fights off a group of corpses but is injured in the process. Finally the alien ship is located and destroyed.
With the jamming signal switched off the team broadcasts the information to the world and the alien invasion is defeated.