The Doctor is eluding the Daleks with his companions Ian and Barbara. He leads them to a manhole to go under where they will be undetected by the Daleks' tele-eyes. Losing their quarry, the Daleks device to test their new Earthmen Detector. When the device reacts, the Daleks realise there are Earth beings in their vicinity only to discover a mere Earth animal: a cat. As the Daleks need to detect humans, they are disatisified with the device's performance and, believing it to be useless, decide to destroy it. Observing the incident from under cover, the Doctor notes that he and his companions have been saved from the Daleks by a cat.