The premise of Devil's Lair is that Dante's account of his travels through Hell in Inferno was basically a true story. Now, the devil has seized the holy grail, and its absence on earth is bringing about the End of Days as the Black Death spreads across Europe in 1349 A.D. A quartet of pilgrims lead by William of Ockham, the famous (and historical) friar and philosopher, undertakes a quest to find the gateway to Hell and retrieve the grail. With him are Nadja, a young German woman accused of witchcraft because she was born with the power to see the future, and Giovanni Boccaccio, the famous (and historical) Italian poet who is an expert on Dante and is expected to guide them through the underworld. The fourth member of their party is Marco da Roma, a former Knight Templar who they find left for dead on a battlefield, suffering from a serious bout of amnesia.