The Survivor

A battered ship near the Neutral Zone turns out to hold Carter Winston, a philanthropist mourned as missing — except the man who returns isn't Winston at all, but a shapeshifting Vendorian wearing his memories. When the impostor seizes Kirk's form and steers the Enterprise toward a Romulan ambush, the crew has to catch the one slip a machine intelligence can't fake: McCoy admitting he might be wrong. Foster's version lingers on how captivity changes the alien as much as it deceives the crew.