In the grand tradition of sixties television, this one swipes its story from a classic film. In this case, the hunting-human-prey plot from "The Most Dangerous Game" (1932). Suave Rory Calhoun lends some class as famous hunter Jonathan Kincaid -- who drops in via helicopter in search of big game. His turban-clad, spear-carrying native assistant Ramoo is played by Harold Sakata (Odd Job himself!) in a throwaway role.
Kincaid holds the castaways captive and selects the agile Gilligan as the object of his hunt. He can't be bribed by the Howells or seduced by Ginger so, the big hunt is scheduled for the following day. The expected hijinks ensue, but nothing funny or imaginative occurs. The series was clearly on autopilot by this point. Plus, the Gilligan-heavy story leaves the rest of the likable cast (the show's saving grace) with almost nothing to do.
Other contemporary shows borrowed the same Dangerous Game premise -- The Outer Limits, Lost in Space, Get Smart, I Spy, et al. -- with far superior results than this limp, run-of-the-island retread. For comparison, just look at Get Smart's creative, well-produced, and funny "Island of the Darned" episode.