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 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.

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.

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

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

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.

Vincent travels to a small town to check a possible link between the aliens and an attack of carnivorous insects.

Vincent is called upon to help avert possible alien infiltration at a government nuclear test site.

Vincent discovers a mysterious computer tape that could offer proof of the alien invasion.

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

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.

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.

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

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.

A dying telephone lineman's fantastic story leads Vincent to investigate a huge industrial complex owned by a famous war hero.

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