The peaceful planet Aneth was once at war with the mighty Skonnon empire, and now Skonnon spaceships demanding tribute have returned to Anethan skies. As the final consignment is being taken to Skonnos, an accident forces the ship off-course. Meanwhile, the Doctor has decided that the TARDIS is in need of an overhaul. After materializing the TARDIS in deep space, he dismantles most of the ship's key circuitry. The incapacitated TARDIS and the Skonnon ship are moving toward a gravity field that could destroy them both.