On stardate 5483.9 (2269) Christine Chapel, the head nurse of the U.S.S. Enterprise's medical department, temporarily became the famed starship's chief medical officer after the male crew complement was rendered helpless by the siren call of the women of the second planet of the Taurean system. Chapel's medical expertise was instrumental in saving the lives of Captain Kirk, Mr. Spock, Dr. McCoy, and Lieutenant Carver, all of whose life forces had been drained nearly to the point of death by the Taurean women.

Despite her undisputed medical competence, Chapel's old affection for Commander Spock remained her emotional Achilles' heel. After being duped by Harry Mudd (stardate 4978.5), Chapel exposed Spock to Mudd's "love crystals,? which briefly caused Spock to fall in love with her, and Chapel's enduring crush on the half-Vulcan science officer turned into short-lived hatred after the drug wore off. A short time later (stardate 5577.7), Chapel nearly drowned in the sickbay aquarium while trying to treat Lieutenant Sulu's leg fracture — after the Enterprise's entire crew had been shrunk to about a centimeter in height by spiroid radiation near the adopted homeworld of the Terratins. Christine Chapel was still part of the Enterprise's medical staff on stardate 7410.2 (2271), but served as a full medical doctor rather than the starship's head nurse.