Both seasons of the 1960s US cult TV series in which architect David Vincent (Roy Thinnes) discovers something that will change his life forever: aliens have landed and they plan to destroy mankind. It is up to Roy to try to convince the rest of humanity of the terrible threat it faces, which proves to be much easier said than done... The episodes comprise: 'Beachhead', 'The Experiment', 'The Mutation', 'The Leeches', 'Genesis', 'Vikor', 'Nightmare', 'Doomsday Minus One', 'Quantity: Unknown', 'The Innocents', 'The Ivy Curtain', 'The Betrayed', 'Storm', 'Panic', 'Moonshot', 'Wall of Crystal', 'The Condemned', 'Condition: Red', 'The Saucer', 'The Watchers', 'Valley of the Shadow', 'The Enemy', 'The Trial', 'The Spores', 'Dark Outpost', 'Summit Meeting: Part 1', 'Summit Meeting: Part 2', 'The Prophet', 'Labyrinth', 'The Captive', 'The Believers', 'The Ransom', 'Task Force', 'The Possessed', 'Counter-Attack', 'The Pit', 'The Organization', 'The Peacemaker', 'The Vise', 'The Miracle', 'The Life Seekers', 'The Pursued' and 'Inquisition'.