Living on the Circle line isn't as much fun as you might think; unless you like rat-burger and frog soup. Civil war has left London in ruins. Years ago, those who couldn't get out retreated into the Underground network, leaving London Topside to disease, packs of wild dogs, and the Scavengers. Now their children are teenagers, and the Underground has got too small for them. Guns are outlawed by the Tobies, but crews from different stations find other ways to fight for what's left. The 'Baker Street Irregulars' get badly burnt by the Paddington 'Bears', and Johny, Callum and Kitty find themselves travelling through some strange and dangerous places in a quest to find a new way of life in what remains of the city. Johny trusts himself to the Ferryman's boat, and travels down-river to fulfil a promise to his dead mother. In doing so he discovers that sometimes it's just our own Fear that keeps us hiding in the dark.