Doctor Who: The Ambassadors of Death

Seven months after it left Mars there has still been no radio communication with the Probe Seven spacecraft, or the astronauts inside it. Eventually a recovery capsule is sent up to rescue the astronauts. But when the capsule returns to Earth it is found to be empty. The Doctor and Liz investigate, in an action-packed novelization based on a TV serial broadcast in 1970, read by Geoffrey Beevers (the Master in "The Keeper of Traken").