Lieutenant Karen Hester-Jones was a Human woman, an officer and a zoologist in Starfleet. For a short time in the 2270s, she served aboard the Federation starship USS Enterprise under Captain James T. Kirk.
Sometime between 2261 and 2267, she dated Captain James T. Kirk for a period of three years, during which he couldn't spend much time with her as he was mostly away commanding a starship. He broke off their relationship poorly and did not contact her further.
She then joined Starfleet hoping it would help her forget him. At night, however, she would still dream of Kirk. By 2267, she had married a man named Bill Jones, and they remained married for six years.
By 2273, Jones chose not to renew their marriage for a second term, having felt he was competing too much with her memory of Kirk. Hester-Jones had risen to the rank of lieutenant and completed research on the mating habits of an indigenous species of primate on Tau Ceti IV which had psychokinesis abilities.
In 2273, she was unexpectedly transferred to the Enterprise. Shortly afterward, the Enterprise discovered the USS Endeavor, which had disappeared in the 2250s. That ship's records revealed a mystery: Hester-Jones' great grandmother had been rescued by the Endeavor on the planetoid Mycena 36 years after her reported death. The starship's crew then began killing themselves, apparently due to a plague of insanity.
Hester-Jones beamed down to Mycena to analyze a large native lifeform resistant to phaser beams and tricorder scans, hoping it might explain the plague. However, it wasn't a plague, it was a form of possession by disembodied transporter test subjects who survived the Hester Project on Mycena. These entities possessed six of the Enterprise crew, then beamed down in order to kill Hester-Jones, believing her to be her grandmother. When the entities spotted the body of Hester inside the wreck of Endeavor's shuttlecraft Kepler, they swarmed into the shuttle. Kirk and Hikaru Sulu destroyed the entities and shuttle with phasers set on overload.