The third book in The Firewatcher Chronicles is Vigil.
The war is finally turning against Hitler, but he has one last secret weapon: flying bombs, sent to destroy the City of London. Among the bomb blasts, Christopher must solve the riddle of the phoenix ring. He journeys back to its source: early Roman Londinium, now surrounded on all sides by the armies of the British queen, Boudica.
With help from a slave girl, Fortunata, Christopher learns the secrets of the ancient Roman fire-watchers, the Vigiles: but unknown to him, a sinister figure from 1666 has followed him through time. To foil a sinister plot, Christopher races across the centuries, to a rebuilt 17th century London, and a newly peaceful Lundenburg, until he and his friends finally untangle the truth.
Vigil will be published in July 2020.