During the Blitz of 1940, many thousands of Londoners were forced to take shelter in the Underground. On the very first day, twelve-year-old William Lumley, his mother, and little sister Aggie are bombed out. Fleeing to the safety of the Tube, they begin a subterranean existence and Will befriends the station marshall, Mr Sands. Although they are sheltered from the constant bombing above, there is great danger underneath the streets. There's a gang of spivs as well as temptation and frustration in the form of Will's fickle cousin Evie. But worst of all an evil, malignant being lurks deep in the tunnels, appearing at night to steal the children away. Only Will has seen the beast, but can he find a way to convince others of the danger amidst the chaos and destruction of war-torn London? This young adult thriller from award-winning author Marc Blake is set during one of the most fascinating and dangerous periods in London's history and will make a perfect addition to any mystery fan's bookshelf.