How extensive are London's secret tunnels? Where do they lead? It's Detective Nick Belsey's summer of trying to behave, and London has decided to go lawless. A stolen vehicle is abandoned, mid-riot, in the shadows of Centrepoint, leading to the discovery of a homeless man bludgeoned to death in his hostel. It seems at first just the nasty edge of a general breakdown, but it leads into the secrets of another age. Under the cover of chaos someone's been doing historical research, visiting 'Deep Shelters', still littered with the remains of 1980s exercises in apocalypse. The trail leads Belsey to a home papered floor to ceiling with photographs of cold-war architecture, maps of underground tunnels, declassified designs. It's soon made clear that his own curiosity is unwanted. He is happy to let state secrets lie. Until it becomes personal. With the police force stretched to nothing, Belsey embarks on a chase through a London on edge deep into the strange, paranoid world of JIGSAW, the government's Joint Inter-Services Group for the Study of All-Out Warfare: the Doomsday Department, as it was known. And finally to the core of its secrets. Deep Shelter is the spectacular second outing for Detective Nick Belsey - a voyage into London's murky underworld, above and below ground.