Procyon's Promise

For hundreds of millennia, the Makers' robot probes had slowly crossed space in search of a faster-than-light drive. To each race encountered along the way, the same offer was made - all the Makers' immense knowledge in return for a fast interstellar drive or help in finding one.

Among the species that accepted the offer was Mankind. And 24th-Century Earth had been made very comfortable because of it But the Community of Nations was about to learn that a promise is a contract - and the Makers would collect for breach.