Eva Grubb is a visitor to the island who came seeking isolation from others because of her looks. Rejected by potential boyfriends and suffering from an inferiority complex, she saved her money and bought the boat to live by herself in exile, but whether she found the island on purpose or chanced upon it is unrevealed. When docking on shore, she is met by the Skipper and Gilligan, who plead for her to rescue them. Instead, Eva tells Gilligan and Skipper they can have her boat, provided they do not reveal the island to anyone. The Professor considers Eva irrational and wants to get her help, but hearing these plans, she attempts to hold everyone hostage on the island, as well as sabotaging the boat by removing the spark plugs.
Ginger and Mary Ann resolve to help Eva's opinion of herself by improving her looks by giving Eva a beauty makeover. Buoyed by her looks, Eva vamps Gilligan, but realizing she'd be over-shadowed by Ginger her whole life, she tries to replace her. She knocks Ginger out with a coconut and gags and ties her up. She then tells Ginger about her evil plans.
At a party, the Howells give in her honor, rushing back and forth to cover both her identity and Ginger, who eventually frees herself and exposes Eva's evil plans. Nevertheless, convinced she could still replace Ginger, Eva sneaks away under cover of dark to return to civilization aboard her boat, with the intention of continuing Ginger's career as "The New Ginger Grant." Her later whereabouts are unknown.
- Eva Grubb was played by actress Tina Louise in a dual role; a stand-in played her in some scenes.
- Tina Louise received a double credit for this episode. However, unlike many who were credited at the end of the episode, the opening scene shows "Tina Louise as Eva Grubb".
- Despite Eva's plans to achieve fame and fortune, it appears she either failed in her attempt or was discovered as an impostor. In "Rescue from Gilligan's Island", Ginger found her career still stalled despite what publicity she had received from her rescue. Furthermore, in a later episode, Tongo the Ape Man mentions recognizing Ginger who had vanished.