Pitt solves this particular mystery by chance - walking along the trackbed one night the "ghost train" passes him and he sees that it is faked by means of a locomotive headlight and a PA playing locomotive sounds running along a cableway strung above the trackbed. This gives him the clue as to the whereabouts of the real train - it was in fact the victim of an elaborate scheme to rob it of a cargo of bullion. One group of robbers demolished the bridge with black powder charges, then staged a holdup of the nearest station; while one of them kept the stationmaster at gunpoint on the floor, another, who remained outside, played a gramophone record of train sounds and flashed a lantern through the windows to give the impression of a passing train, misleading the stationmaster into thinking that he had failed to prevent the train tumbling off the downed bridge. In fact another group of robbers had hijacked the train further up the line, diverted it along a disused spur into an abandoned underground quarry, and then blown up the entrance to the quarry concealing the train and allowing them to remove the heavy load of bullion at their leisure through the quarry's old ventilation tunnels.