Spock Must Die!
James Blish
 The Klingon Empire manages to imprison the Organians and begin another war with the Federation. Captain Kirk and the crew of the USS Enterprise find themselves far behind enemy lines. Dr. McCoy expresses his fear that he was killed the first time a transporter disassembled his original body and created a replacement in a new location. Scotty attempts to create a new method of teleportation that uses tachyons. He later uses this experimental method to send a duplicate of Mr. Spock to Organia via a souped-up transporter beam, without having to travel through Klingon space. Something goes terribly wrong, resulting in two Spocks returning. One of them has to be destroyed...but which one? The novel is notable for an elementary public exposure of tachyon theory. For a similar duplication of Captain Kirk, see the Original Series episode "The Enemy Within".