Charles Pagan and Dick Baron, who served together in WWI, embark on a walking holiday in the Vosges Mountains in France, in 1930.
En route they meet Cecil and his sister Clare who is recovering from the loss of her fiance during the war.
Pagan and Baron pitch camp at a guesthouse, but the strange behaviour of locals piques their interest in the surroundings: in particular the old battlefield nearby.
They express an interest in visiting it and are told by their host in no uncertain terms that it is not the place to go at night.
When they discover they have been locked in their bedrooms, the pair lose no time in putting a rope out of the window and shinning down it, intent on exploring the forbidden territory and viewing the apparition Pagan thinks he has glimpsed briefly by moonlight. Pagan, like W. F. Morris's preceding novel Bretherton, is a mystery story, but one which could only have been written as a result of the war.
Bretherton himself is mentioned in passing by his brothers in arms.
It is exciting, spine-chilling, funny, and romantic, but the Great War taints all these elements like a colour filter on a camera.
The war is only a decade away and wounds, both mental and physical, are raw.
The novel works brilliantly as a thriller in its own right, and but also a commentary on post-war Europe.