Procyon's Promise — Michael McCollum

For millennia, the Makers' Life Probes explored the farthest reaches of space in search of the secret behind faster-than-light speed. In the 22nd century, the people of Earth made a pact with this far-flung civilization -- all of the Makers' intelligence in exchange for help in their mission.<br>

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Three hundred years later, descendants of the original Procyon expedition have returned to Earth in a starship. They find a world that has forgotten the generations-old contract.<br>

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No matter. The returning colonists have overcome far greater obstacles in their single-minded drive to redeem a promise made before any of them were born…