"It's the end of term at Hyperspace High and John Riley and his fellow students are in the grip of revision fever. Suddenly John's best friend, Kaal, has a fever for real - he's caught the deadly Zhaldarian flu! Soon the whole school is under threat. The only possible cure lies in a distant nebula. John is determined to save his classmates, but will anybody be brave enough to join him?"--Page 4 of cover.