The Survivor

Near the Romulan Neutral Zone, the Enterprise rescues the pilot of a small, damaged craft: Carter Winston, a celebrated philanthropist and trader who vanished five years earlier. His fiancée, security officer Lt Anne Nored, is serving aboard, but Winston coldly breaks off their engagement. The visitor is really a Vendorian, a shapeshifter working for the Romulans. It overpowers Kirk, takes his form and orders the ship into the Neutral Zone, where Romulan warships are waiting. Kirk exposes the deception, but the alien has already disabled the deflector shields. As the Romulans attack, it makes an unexpected choice, turning itself into part of the deflector system to shield the ship, and the Romulans withdraw. The Vendorian explains that the real Winston died after crashing on its world, and that in absorbing his memories it came to share his feelings for Nored. It is placed under arrest, and Nored volunteers to guard it.