"Someone is draining the Overworld oceans of resources. At the same time, a priceless gemstone has gone missing from the new Capital City Museum. The troopers of Battalion Zero must pool their brains, brawn, and every bit of luck they have to get to the bottom of both mysteries. Could it be a ploy by the Griefer Imperial Army to draw Captain Rob and his cavalry members away from the United Biomes of the Overworld capital, which they've risked their very identities to defend? Or is it theft on a scale so grand that only the deepest oceans can contain it? The battalion members must pull off the perfect heist, working together to recover the UBO's greatest treasure. But when an old friend resurfaces, loyalty to the UBO cause will be tested again"--Back cover.