After being expelled from a number of expensive schools, R.J., Robin Masters rich, careless, teenage nephew, arrives at the Estate to be reformed and educated by Higgins. R.J., however, has other ideas and decides to impersonate Thomas after being impressed by his adventures. Hired by a woman to find the only witness to her husband's murder, R.J. manages to get Thomas and everyone else involved in the case targeted for death by the men who killed the woman's husband.

Magnum is to spend a week aboard a luxury cruise ship guarding an Amakua, a valuable wooden Hawaiian statuette recently purchased by Robin Masters, to be displayed on the liner while en route to the Hilo Museum. But Magnum and Higgins find that Apollo has been shot and seriously wounded after thieves attempted to steal the artifact from the Estate. Expecting the would-be robbers to try again during the cruise, Magnum secures Rick and T.C.'s additional help in guarding the artifact, but they find themselves on-board with a shipload of suspects, all potential thieves of the Amakua.