Leaving Honey Island and continuing via another ship, our heroes are surprised to see Porter, the chief purser from their previous ship, on board! Actually, it’s not the same person: this new Porter explains that he’s an identical cousin of the one they met previously. He then tells everyone of the upcoming Marine Cup Tournament, and Ash and Iris can’t wait to be part of it!
They also meet Mrs. Ripple, one of the foremost gem collectors in Unova, who is planning a showing of her gem collection after the tournament—and her Purrloin, who (like all Purrloin) gives Cilan the heebie-jeebies. When Mrs. Ripple graciously agrees to show our heroes her collection privately, everyone is especially taken with the Eye of Liepard, the biggest known gem of its kind in the world. Although fellow collector Mr. Shaw is determined to purchase the rare gem, Mrs. Ripple refuses, much to his frustration.
The Marine Cup Tournament begins on the ship’s main deck. An unfamiliar Trainer named Teaque and his Vanillite quickly eliminate Iris and Axew, and the final round is Ash and Pikachu versus Teaque, who’s using a Galvantula this time. Meanwhile, who should break into the locked gem room but Mr. Shaw, who just has to have another look at the Eye of Liepard...
Back on deck, Galvantula’s Thunderbolt apparently goes awry and strikes the ship’s electrical system, causing a temporary blackout! Once the power is restored, Ash and Pikachu win their battle—and then, out of nowhere, Mrs. Ripple’s Purrloin launches itself at Teaque in a furious attack! Ash manages to pry Purrloin off his opponent, and it runs away. Mrs. Ripple and Porter go looking for it, and when they decide to check the gem room, they find that Mr. Shaw has broken in and the Eye of Liepard is missing! Mr. Shaw insists it was already gone when he got there, but considering his extreme interest in the gem, he’s still the primary suspect.
But after a thorough search, Porter reports that they couldn’t find the stolen gem anywhere in Mr. Shaw’s things. It’s a mystery—and as it happens, one of our heroes is a big fan of mysteries. Just like that, Connoisseur Detective Cilan is on the case! He starts to piece together the evidence, and quickly realizes that even though he doesn’t like Purrloin, it was in the room during the blackout when the gem was stolen, so it’s his best witness. And given Purrloin’s attack on Teaque after the blackout—plus the water spot on the rug right next to the table that held the gem—he has a conclusion: Teaque must have caused the blackout on purpose, then sent his Vanillite into the locked room through the air ducts to steal the Eye of Liepard!
The case is solved, the gem is returned, and the adventure on the high seas continues!