The ship Meridian Star departs eastern Russia unknowingly carrying a pair of containers with radioactive cesium chloride. The vessel is hijacked and scuttled in Micronesia near the Mariana Trench, and the crew is murdered. A huge insurance claim results, and Jack, an accomplished deep-sea diver who works for Hendley Associates, is there to investigate. The hostile Chinese learn it’s there and want that illicit cargo. Meanwhile, the Naval Undersea Warfare Center discovers a huge, mysterious object in 600 feet of water. At that depth, the pressure is unsurvivable without complex special equipment, which is vintage Tom Clancy. Whatever the strange object is, it’s “not a ship…not a submarine…not an aircraft.” On the side is a faded hammer and sickle and Cyrillic letters that spell Siren. Ryan teams up with Navy divers, and they look for a way to safely enter and explore the object. They discover that the underwater contraption has thermonuclear warheads attached, left and long forgotten by the USSR. If the warheads explode, they could still achieve their apparent purpose—to trigger a tsunami and destroy Guam, which is strategically important to the U.S. The Chinese know it too, and the race is on to take control. The result is plenty of high-stakes undersea action, where death can come from a bullet, a knife, or a sliced air hose. But there’s action on land, too. Navy master diver Carla Bennett and Jack take on a surprise assault in a hotel where Carla shows off stellar fighting skills—better than Jack’s. These two aren’t the only heroes here, as there’s a well-balanced cast of characters, all brave and likable. And of course—of course—where there’s a bomb, there’s a ticking clock.