Author:  James Blish

Published:  February 1970

Publisher:  Bantam Books

Number in Series:  1

Timeframe:  During The Original Series

From Bantam Books:

“When a transporter experiment goes horribly awry, suddenly there are two Mr. Spocks. One is the true First Officer of the “Enterprise.” The other is his complete opposite, a traitor whose very existence poses a grave threat to the crew, the ship, and the Federation itself. One of the Spocks must die. But which one?”

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