The chauffeur of eminent scientist Sir Henry Felton arrives to collect his boss's Rolls-Royce from its service at a local garage. The garage is now under new management — namely, a group of bald-headed men — and the chauffeur discovers that the car has been fitted with darkened rear windows free of charge.
When Sir Henry mysteriously disappears from the back of the car en route to a lunch meeting with the Doctor, the Time Lord investigates and discovers that Sir Henry is working on an advanced project concerning matter transmission.
The Doctor re-enacts Sir Henry's journey and is transported to a secret bunker beneath the garage, thanks to a matter transmitter built into the car's door panels. He finds Sir Henry being held prisoner by the bald-headed men, who are peaceful aliens from Proxima Centauri in the Crab Galaxy. They have anticipated Sir Henry's discovery and want Earth to be denied knowledge of matter transmission. After warning Sir Henry that the guilt will be his when Earth spreads warfare across the galaxy, the aliens escape via the matter transmitter — leaving the Doctor and Sir Henry to think about whether his discovery will indeed be used as he wishes and if Mankind is ready for it. Sir Henry makes his decision there and then: ordering the matter transmission equipment and his notes to be destroyed immediately.
- If there should be a moral to this story, it must surely be that any scientific breakthrough can be used for good or for evil purposes.
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