The second in the Blackwood and Harrington series. London 1899. Something strange is happening on the London Underground. The ghosts which haunt the platforms and tunnels are being seen much more frequently than usual, and it seems that they have become angry and frightened for some reason. There is, apparently, something on the network of which even the dead are afraid, and the train drivers and other staff are becoming increasingly reluctant to work there. The new atmospheric railway is being installed, and the railway companies are demanding that the mystery be solved before their investments go up in a puff of steam. When a train driver named