The Romans are leaving London and Britain in 410AD as the empire withdraws to defend its territories in Gaul against Germanic tribes. Constantine, the Emperor of Britain, faces execution under orders from Honorius, whose belief is that failure deserves death. Living near the Forum but drawn to the River Lea, Constantine seeks escape in a landscape regarded by Romans as a place where ancient British spirits remain strong. To avoid assassination, he throws himself into the River Lea and is carried downstream to Bog Island near the Thames. There, he encounters a community that has resisted Roman influence and remains connected to traditions of the ancient Britons. Through this community, Constantine reaches Elswick on the Walthamstow Marshes, a place accessed by a time portal known as the Black Path along the Philley Brook. The inhabitants of Elswick live in 1665 and possess the ability to travel through time. Constantine becomes drawn to this power. In 2027, Billy Gilts manages West Ham United as the club struggles near relegation. Under pressure and unable to sleep, he becomes dependent on Zopiclone, which allows him to connect with a dream guide revealed to be Constantine. Constantine's spirit, tied to the River Lea after his death, carries regret from 1811 when he failed to prevent the Ratcliffe Highway murders. Billy works with Morwenna, a medium, and Jill Scott, a football pundit. Through swimming in the River Lea, Billy communicates with Constantine and discovers a link between his ancestry and the murders. Determined to change history, he seeks the Black Path with the help of John Rogers. The story concludes with West Ham avoiding relegation as Billy prepares to travel to 1811 to restore his family's reputation and redeem Constantine, while a Russian drone strike hits Dungeness nuclear power station.