Carrington intends to turn the world against the aliens by revealing them on TV.
The alien captain demands the return of the ambassadors or he will destroy the world.
The Doctor prepares to pilot the Recovery 7 ship into space.
Quinlan, the Doctor suspects, is part of the conspiracy, but Quinlan is killed.
The Doctor deduces that the occupants of Recovery 7 were not human.
Recovery 7 returns to Earth but the UNIT convoy transporting the capsule is ambushed.
All contact has been lost with the Mars Probe 7 space mission.