Matthias Fitzosbert, illegitimate son of a parish priest, has a unique relationship with Rosifer, the fallen angel--the spirit he loves yet hates, strives to placate yet ultimately must flee. The story of Matthias is played out against the vivid panorama of the Middle Ages--the fall of Constantinople; the last throes of the Wars of the Roses; the terror of witchcraft; the loneliness of the Scottish marches; the battlefields of Spain; and finally, the lush jungles of the Caribbean, where the Rose Demon and Matthias meet for a final deadly confrontation.