Steve, Matt, and Jenny board their very first cruise ship prepared to relax, have fun, and eat a lot of food. But on their first night out at sea, they discover the ship holds a secret. Many years ago, a smuggler hid a very expensive jewel somewhere on board, leaving behind a letter, written in code, as the only clue to its location. Excited at the possibility of solving another mystery, the trio begins the investigation only to unwittingly draw the attention of three very dangerous men and one mysterious deckhand, all of whom seem interested in finding the diamond for themselves. With only three days to find the gem or lose it forever, the three kids race against the clock to decipher the clues and discover the gem, while keeping themselves and their parents out of danger. BookLife Review: Arango's delightful tween sleuths return in her latest Decoders offering (after The Dragon's Horn ), this time to tackle a puzzling cruise ship mystery. Steve Kemp's parents booked a four-day vacation on the Ocean Adventure and invited his best friends, Jenny Reed and Matt Peterson, along for the ride. The trip involves a fun challenge: find the mythical Ruby Diamond and win a free cruise every year for life. But what the Kemps don't realize is their young charges aren't just interested in this diversion; they've discovered that the Ruby Diamond is real--and it's still on the ship. Arango's fast-paced thriller is full of high-stakes tension, and young readers will feel as if they're cruising alongside the trio as they sift through clues, red herrings, and their fair share of nefarious characters. The adventure starts with a story of the ship's prior security officer, Hugo Lamberto—a gem smuggler who was offered one million dollars to transport the 100-carat red diamond on board. Steve, Jenny, and Matt quickly learn that the rumors of Hugo hiding the diamond on the ship may be more than just rumors--and Hugo's coded letter to his brother, discovered after he died, serves as their first real clue. But the Decoders can't stay hidden forever, and they eventually come to the attention of Nico, the ship's deckhand and cousin of the Lamberto brothers, who recognizes that these smart, resourceful kids may be able to help him find the genuine jewel. Solving clues that range from pop culture references to Greek myths, the trio skillfully juggle several interconnected mysteries, one of which offers something very rare indeed: official recognition for their stellar deductive skills. The Ruby Diamond can be read as a standalone, but middle-grade mystery fans will find that Arango's Decoders series, with its combination of fun, friendship, and action-packed storylines, will both challenge their wits and engage their sense of adventure.