After an alien is captured in a small town, Vincent warns the townspeople, who assume their captive is a madman.

A Russian ambassador summons David Vincent after he finds that a burglar caught inside the embassy is an alien.

While investigating the theft of a mysterious cylinder from the site of a plane crash, Vincent is captured and suspected of being an alien.

The invaders and Vincent race to capture a wounded alien whose touch brings on freezing death.

David's brother, who also thinks he is crazy, is kidnapped by the aliens who intend to destroy the oxygen in our planet's air.

The invaders frame Vincent for the death of an owner of an electronics plant who had made discoveries about the aliens.

Vincent attempts to thwart the alien infiltration of a Air Defense Command Unit.

Vincent battles, then destroys an alien guard and captures one of their spacecraft.

An architect's close encounter with a spaceship leads him to investigate a small town's hydroelectric plant.

Vincent is called on by a renowned electronics expert who fears he may soon be abducted by alien invaders.

The aliens take David Vincent up into their spaceship and then attempt to prove they have nothing but peaceful intentions by showing him what they've done to a desert valley. But all is not what it seems.

Vincent is contacted by a meterologist to help investigate the suspicious nature of a hurricane along the Eastern U.S. coast.

Vincent helps a security official investigate the deaths of two lunar astronauts in a strange red fog.

Vincent is horrified to learn the invaders are using strange seed spores that after cultivated will develop into full-grown aliens.

When David Vincent brings an injured alien into the doctor for treatment, the patient's x-rays reveal odd results. While David works to alert the authorities, the aliens conspire to destroy both evidence and witnesses.

David Vincent is kidnapped in a sneak attack on his new found alien-fighting allies, and he must try to escape an alien installation with a human psychologist.

David Vincent is called in to aid a huge magazine publishing company that has been experiencing disruptive behavior in its company heads, and David believes that the aliens are behind the troubles.

David deceives the aliens that he is willing to work with them for a fee, all the while with a plan of attack in mind.

David Vincent arranges a meeting between the alien leaders and an Air Force General, who secretly plans to drop a bomb on the alien leaders despite the fact that many innocent people will die in the process.

Racist issues arise between David Vincent and the Baxters, a black couple, when David produces evidence that another African American in line for an important position with the space program is actually an alien.

A pair of aliens who want to return to their home planet and make a political argument against the invasion of Earth ask David Vincent to help them elude an intensive police manhunt.

With the assistance of Vicki, a nightclub stripper, Vincent continues his search for an alien spacecraft.

Vincent discovers that a school is being used by the aliens as an indoctrination center.

David Vincent meets with an eminent astrophysicist who has proof that aliens are invading the planet.

Vincent's search for aliens lead him to an underwater sea lab.