Eve McHuron was one of three women being transported to Ophiucus III as a wife in 2266. Originally from a farming planet, she had no marriage prospects, as the farms were tended by automatic machinery and her brothers.
She was introduced to the Venus drug by Harcourt Mudd, the architect of this scheme; the drug enhances a user's attributes. Her natural allure was boosted by this chemical. She was brought to the USS Enterprise after the cargo ship Mudd was using was destroyed in an asteroid belt.
McHuron's conscience worked against Mudd's plans – when he assigned her to seduce Captain Kirk, she could not carry out that plan. She also viewed the Venus drug as a trick and Harry Mudd as a con man. Worse than that, she was actually attracted to Kirk.
Mudd's scheming ultimately brought her to the surface of Rigel XII, where the Enterprise had stopped to collect replacement lithium crystals. There, she met Ben Childress, the chief miner. Unhappy for a number of reasons, she fled his home into a magnetic storm on the planet's surface. Despite the risks, both Childress and Kirk went after her; it was Childress who eventually found her and returned to his home with her.
She and Childress sparred verbally – and this grew angrier when the Venus drug wore off, leaving her far less appealing, and Childress angry at Mudd's trickery. After taking a dose of the drug that turned out to be a placebo, and becoming beautiful again despite that, she realized that self-confidence had as much to do with appeal as the Venus drug did. Childress asked her to remain, "at least for the day", so they could talk. (TOS: "Mudd's Women")