You've already discovered the Titanic. How can you possibly follow up? If you're the intrepid undersea explorer Bob Ballard, you set out in search of the fabled ship's twin: Britannic. The most luxurious of its line, Britannic was redesigned to benefit from the lessons learned from the Titanic disaster. Yet, four years later, in its new guise as a World War I hospital vessel, Britannic too became a casualty- sinking to the bottom of the Aegean in half the time of the Titanic. Dive to the depths with Ballard, his team of historians, and a shipload of high-tech equipment: a U.S. Navy nuclear submarine, powerful sonar, and state-of-the art cameras. Titanic's sister ship- another symbol of a gilded era- is surrounded with mystique: Why did its safety fail to operate? Was it felled by a malicious torpedo attack, or did it stumble on a mine? And what kind of shape is the majestic steamer in now? Ballard is hoping the hidden hull with give form to his dream: to create the world's only virtual undersea museum, luring visitors to the internet. The first ghostly images look promising- but can the ambitious crew really expect to find this mysterious vessel still intact?