Raumpatrouille - Die phantastischen Abenteuer des Raumschiffes Orion - Season 1 (1967)

A human commander tries to defect to the Frogs, later saying he doesn't remember the incident. When the Orion is ordered to the sector where it took place, similar things happen to the Orion crew and loyalties are put to the test.

Variations in the sun's energy output threaten the Earth's climate. The Orion crew investigates and discovers a long forgotten colony of humanity which may be responsible.

The Orion takes aboard a writer looking for inspiration for his next novel, which doesn't make things easier when the crew encounter a colony of outcasts with dangerous ambitions.

Unusual behavior by high-ranking intelligence officials makes Commander McLane suspect a conspiracy. No one listens to his warnings until it is too late: the invasion by the Frogs is already underway.