After the death of his father in a car accident a year ago, Will Boone is struggling to come to terms with his life. A chance encounter with a mysterious tramp called Ari, makes things even more baffling. Ari tells Will he has a message for him – from his dead father.
When Will digs deeper he discovers that Ari is a member of a band of new age travellers – The Watchers, a group of fallen angels, cast out of heaven in the 'great war.' They have been sentenced to travel the earth, making up for their past sins by helping mankind. But they are pitched against a second band of angels, led by the dark and sinister Lou, who have devoted themselves to mischief and who have set their sights on adding to their considerable tally of souls by casting Will's father into the deepest pits of hell.
With the help of Ari and the other Watchers, Will must work to prevent this from happening – and the Watchers are able to equip him with some very special skills to help him achieve his aims. But when it comes to the final showdown, can they prevail against the powerful forces of evil?