MORE THAN SEVEN MONTHS HAVE PASSED SINCE Mars Probe 7 left the surface of the Red Planet, yet nothing has been heard from the astronauts on board. With the stricken vessel now orbiting the Earth, Space Control has dispatched Recovery 7 to investigate.
As astronaut Charles Van Lyden enters the silent ship, there is a deafening electronic blast and his communication ceases abruptly. Back on Earth, the Doctor identifies the disturbance as a message of alien origin and correctly deduces that there will be a reply, which is duly transmitted from a disused warehouse nearby.