In the shadows of Walton Hall a demon lurks. His name: Mephistopheles. In 1586, young John Striven struck a bargain with him in return for help against his murderous foster brother. Nice work for a demon - or it should have been. Because somehow, his plan to trap the 12-year-old went wrong. All he needs now is another soul, in similar desperation, to call on him. Enter 13 year-old Henry Fowst. A pupil at Northwell School, Henry longs to win the Northwell History Essay Prize. Exploring the school's sixteenth century library, he stumbles across the diary of a boy his own age beginning this 20th day of Januarie, 1586... Soon Henry is absorbed in John Striven's struggles with his jealous foster-brother, Thomas Walton, who, it seems, will stop at nothing to be rid of him. Then matters take a darker turn. Battling to escape his own enemy, Henry finds his life beginning to imitate John's and when the diary shows John summoning 'an Angellick Spirit' to his aid, Henry eagerly tries the same. Unfortunately, calling up Mephistopheles lands both boys in greater danger than they'd ever bargained for...