It's murder most foul when Higgins is struck on the head with a stray croquet ball right before a lavish Great Gatsby-themed costume ball is scheduled to be held atRobin's Nest. As Magnum rushes to keep things under control, some priceless jewels go missing, and an addled Higgins finds himself the prime suspect in the murder of one of the guests.

Magnum finds himself locked into a mystery when a bank teller accidentally traps the two of them in a time-release vault at Robin Master's bank. Inside, they find large amounts of counterfeit bills, which the teller believes is proof that her father, a world-famous painting forger, is back in business.