Invisible Enemy

S2 E7: A flight to Mars succeeds - but the astronauts don't come back. A second expedition sets out to discover why first men on Mars landed safely but never returned. They find wreckage of the first craft but there's no sign of life. One of the crew mysteriously disappears in a sea of sand. A trace of blood leads the crew to suspect an invisible enemy. Investigation of the strange sea imperils the flight Commander and his crew exert heroic efforts to save him from a horde of monsters that inhabits the region.