The Wheel. A ring of ice and steel around a moon of Saturn, and home to a mining colony supplying Earth. It’s a bad place to grow up**.** The colony has been plagued by problems and there are stories of mysterious creatures glimpsed aboard the Wheel. Many of the younger workers refuse to go down the warren-like mines anymore. And then young Phee Laws, surfing Saturn’s rings, saves an enigmatic blue box from destruction. Aboard the Wheel, the Doctor, Jamie and Zoe find themselves caught in a mystery that goes right back to the creation of the solar system. A mystery that could kill them all.