Marine biologist and cameraman Rick Rosenthal has been filming in the ocean for decades. But one spectacle has eluded him and every other filmmaker until now – the amazing “great vertical migration”, when billions of animals rise from the depths to the ocean’s surface. Yet this extraordinary event happens every night, in every ocean. Now for the first time, Rick Rosenthal will capture it on camera. But to do so, he must risk the dangers and face the challenges of filming in the open ocean, in the dark. When he succeeds, Rick unlocks the secrets of a bizarre and alien world – a world driven by survival to remain forever in the oceans’ shadows.