Sent to intercept the Third Doctor at the International circus, two Autons disguised themselves as policemen to take the Doctor and Jo Grant to a quarry to kill them. However, the Doctor saw through their disguise and caused the police car to crash. The police car's passenger door was blocked in the crash and the Auton tried to shoot the Doctor and Jo as they ran. The Auton policemen managed to get out of the car and started to search for their escaped prisoners.
The Brigadier, Captain Mike Yates and another UNIT soldier arrived and also started to search for the Doctor and Jo. The Autons shot the soldier and, as a last resort, Mike Yates rammed his car into the Auton, causing it to fall off a cliff. The Doctor, Jo, the Brigadier and Yates managed to escape in the car.