The crew aboard the USS Elmira are working on a project, code named Operation Honeymoon. At the operation's core is the testing of the Magnetic Analyzer Computing Synchrotron, or MACS for short, which is a smart computer designed to do among other things determine where missiles are going to land. Civilian Jason Eldridge is the scientific mastermind aboard in charge of MACS' operation. His friend aboard, Lieutenant Ferguson Howard, sees other possible uses for MACS. He wants to know if MACS, if given the proper data, can accurately predict games of chance, such as those found in casinos. After discussing the situation, Fergie and Jason decide the game which MACS can predict the most accurately is roulette. They decide to test MACS' abilities, and possibly get rich, at their next port of call where there is a casino, namely Venice. They plan on using a system of Morse Code light signals from the ship to shore to transmit the information. Although they go ahead with their plan, they are sidetracked by female distractions. Jason runs into his old girlfriend, hot dog heiress Pam Dunstan, who he left three years earlier because he felt he couldn't support her in the lifestyle to which she was accustomed. He is dismayed to learn that she is in Venice to get married to the pompous Tommy Dane, who works for the State Department. And Fergie meets a beautiful young girl named Julie Fitch, for who he instantly falls. He doesn't tell her of his naval occupation since her father is a naval admiral also in town. But problems for Jason and Fergie really begin when Admiral Fitch sees the transmission of messages to and from the ship, which he believes is enemy communication.