What happens when a police box materializes on the runway of Gatwick Airport? Why the police come over and retrieve it. The Doctor and Companions arrive in 'modern' Gatwick Airport, leading Jamie to believe they're being attacked by flying beasties. As they're running around Polly discovers a murder. As the story progresses it gets weirder and weirder. The murder was conducted using a weapon which electrocuted the victim, leaving burn marks and scorched fabric, and why was an unused Spanish postage stamp in his pocket? Curiouser and curiouser my dear Commandant. The Commandant is in charge of the airport and doesn't believe this poppycock of aliens from a different planet stealing young people, shooting ray guns, etc. Ben and Polly both are abducted by the aliens and disappear, leaving Jamie & the young lady he meets, Sam, and the Doctor, to figure it all out. Seems these aliens had a problem on their planet and they're slowly dying out, and their plan is to steal earthlings to grab their life force. The aliens in their original form are 'faceless' and can be processed through a machine to take on the identity of others, making them a kind of Chameleon. They are luring young people into flights to holiday destinations but the trips are fake and instead the people are brought to an orbiting satellite, and it's due to return to their home world. But the Doctor manages to get on board and change the situation, convince the aliens to not follow through with their plan and to return everybody.
The episode marks the departure of Ben and Polly, due to it being the same day as when they met the Doctor. They are home and they want to return to their lives.
At several times during the episode the Doctor is explaining this otherworldly plan to the officials and sitting in their shoes it must have sounded like the worst of supermarket junk newspaper stories ("Space aliens stole my husbands body and took his form")...
July 20th, 1966, is noted as the busiest day for the Doctor in his time on Earth. The First Doctor defeats the War Machines and WOTAN.