One wrong move could mean the end of the world! What did Professor Childermass's eccentric brother mean by the mysterious riddle he attached to his will? And why does he insist the professor spend the summer on his deserted estate in order to earn his inheritance? The professor, Johnny Dixon, and Johnny's friend Fergie are determined to find out. But when they journey to the ramshackle mansion, they make a horrifying discovery. Unless they unravel the baffling riddle fast, an evil madman will succeed in unleashing a force so powerful it could destroy the entire world!