Herrick and Slocum find a message in a bottle that alleges a ship thought to have been lost at sea due to a fire was scuttled to cover up illegal munitions trading. Instead of turning the note over to the authorities, Herrick launches his own investigation placing him and his friends in deadly peril.
While attending an auction, Captain Herrick buys a Victorian sideboard and Jonathon Beale purchases a statuette of a horse, little realizing that the pieces where involved in a theft from an Italian art museum.
On a tuna hunting trip, a young man is included in the crew the rest of the men resent, believing he was responsible for accidents on other ships in the past. They set out on an uneasy course, made worse by the supposed jinx's popularity with the ladies.
Captain Ed Conway, an old friend of Captain Herrick's, buys an equally ancient tugboat hoping it will be the foundation of his own company. Conway is mystified when flashy George Mallory offers to buy his old tub for more money than it's worth and then concerned when he finds his ship sabotaged after turning down Mallory's offer.