Five years earlier, the Keating coal mine had been rocked by a terrible disaster that claimed dozens of lives. After some time, however, someone became convinced that the tragedy was not caused by natural causes, but by the hand of man. What is certain is only that the ghosts of the miners seem to haunt the site of the massacre, and are capable of taking revenge. In fact, a series of mysterious murders causes death among those who held positions of responsibility in the management of the mine. Who is the serial killer? And why does it strike? Zagor takes it upon himself to investigate... Engineer Joss Beaumont, believed to have died in a mining disaster that killed dozens of workers in the Keating mine, actually survived. Beaumont has discovered that the victims are largely attributable to the owner of the extraction plant, the sinister Milton Miller, who sealed the openings of the excavations to prevent the fire from burning the coal that was the source of his wealth. Hence his desire for revenge which materializes in a series of explosive and incendiary attacks against collaborators of the mining company and some logistics structures. Chemical expert that he is, Beaumont designed the formula for "beaumontite", a deadly explosive. Sheriff Baker, marshal of Coalbridge, the town that hosts the headquarters of Miller's company after Keating's abandonment, which has become a ghost town, has asked for Zagor's help to capture the attacker, whose identity he does not know, also because he covers his face with a disturbing mask. Milton Miller does not cooperate with the investigation, worried that someone will discover his many shady dealings and also his responsibilities in the Keating catastrophe. Spencer, his brother, instead provides the Spirit with the Hatchet with all the information he has, in the hope that the attacker will be captured before he and Mary, Milton's daughter, end up among the victims. Mister Miller, meanwhile, gives orders to his men to eliminate Baker and Zagor before they discover anything. In fact, Zagor discovers that Beaumont wants to blow up a dam that operates, with water pressure, a sawmill useful to Miller for his activities. Miller's right-hand man, O'Connor, meanwhile plots to rob his own boss, stealing the wages intended for the miners. Joss Beaumont's endless revenge continues to burn like the fire that has been burning from within the mountain above Keating for five years (since the mining disaster that cost the lives of so many workers). Precisely the slow consumption of coal has dug enormous underground cavities which the engineer Beaumont, driven mad by the tragedy he barely escaped, wants to collapse with the deadly explosive of his own manufacture, the "beaumontite". To hit Milton Miller, the owner of the mining company that he considers responsible for Keating's catastrophe, in his dearest affections, Joss kidnaps Mary, his daughter, attracting all the protagonists of the story (Miller, Zagor, O'Connor and his men) to the ghost town, where the last act of the tragedy takes place...
