In her 2005 blockbuster, “Labyrinth,” Kate Mosse plunged her protagonist into a cave in the French Pyrenees that turned out to be a portal to the medieval past. The plot abounded in skeletons and secret symbols that eventually revealed the fate of the region’s Cathar people and – somewhat predictably – the wonders of the human heart. In “Sepulchre,” Mosse returned to the Languedoc of 1891 where the legend of a Visigoth tomb, a demon and a tarot pack led visitors into the mystical past. The author is now writing “Citadel,” the final book in this trilogy, but in the meantime, “The Winter Ghosts,” a slim and affecting novel, once again reanimates the history of France’s persecuted Cathars.

This time around the innocent abroad is Freddie Watson, a sensitive young Englishman who travels to the Pyrenees in 1928 to recover from the death of his brother in World War I. Freddie is following medical advice and his own forlorn belief that in France there will be “no one to disappoint.” Because, as his parents’ mourning reminds him, Freddie is not the man his brother was. “It was a thin line between heroism and arrogance,” Freddie recalls, “and George had always walked it.” But when George’s ghost appears, unannounced and fleeting, Freddie is left both comforted and newly bereft.

A larger haunting awaits him, though, as we can tell from Mosse’s portentous descriptions. “The sun falls early in those high valleys,” Freddie notices as he approaches a mountain village, “and the shadows were already deep.” Like any self-respecting hero, he rashly drives across a mountain pass in bad weather, lured by “a whispering, almost like singing” that he senses in the air. “The others have slipped away into darkness,” the voice calls, and soon Freddie is knocked briefly unconscious when his car leaves the road. He struggles on foot through the woods, hearing the voice and glimpsing a mysterious woman on a hillside before reaching a village whose bloody history will eventually explain these apparitions.

Here Freddie’s adventure becomes a fairy tale as much as a ghost story. “The air was thick with smoke from the open fire burning at the far end of the room,” he observes when he arrives at the village feast. “A thousand candles scattered light and shadow from metal sconces on the walls, ever shifting, ever dancing.” An ethereal beauty named Fabrissa enthralls Freddie and then astonishes him when she begins to speak of his dead brother. Suddenly, sword-wielding soldiers appear.

Mosse devotees will guess correctly that Freddie’s search will lead him to long-buried evidence of an ancient crime and to personal redemption. It is a familiarly comforting conclusion to a stark yet lyrical tale.