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.

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.

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

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

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.

A hysterical hotel manager tells Vincent aliens are taking over his hotel.

Despite Vincent's warnings, a nurse tries to help an injured alien survivor of a saucer crash.

A man seek's Vincent's aid after he is arrested and put on trial for murder after the incineration death of an alien.

While investigating the Invaders susceptibility to minor human ailments, Vincent unknowingly is taken aboard an alien spacecraft.

In Part I of this two-part episode, Vincent uncovers a diabolical alien plot to destroy all of the world's leaders.

In the conclusion of a two-part episode, Vincent must defuse an experimental rocket that if ignited will destroy all heads of state gathered at a world summit meeting.

An old college buddy sends David Vincent an urgent message, without any further details other than that it is important. When David arrives, Ted has been brain washed so that he can no longer remember why in the world he'd wanted to see his friend. It soon becomes obvious that the aliens are using mind control of some sort.

David Vincent joins forces with the mob when the aliens inadvertently take their illegal shipment of drugs.

The aliens’ experiments with artificial human emotions go awry when one of their subjects, prone to homicidal rages, defects to David Vincent’s side.

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.

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.