Rush hour on the underground and a killer is at large in London, striking apparently haphazardly in a series of vicious attacks. Andy Brewster, ex-SAS, on sick leave from active service in Iraq, works undercover for the Metropolitan police with his bomb expert partner, Burgess. Together they must find the killer before he strikes again. So far the victims have all been women with no apparent connection. Beth Hardy, former caterer who now runs a gourmet food shop; her daughter Imogen, dancing at the National; sad Celeste with her terrible secret; widowed Margaret, in to shop; and American tourist, Ellie, stranded there alone. Each of them regularly travels by tube not knowing they could be potential victims. When the July 7 bombs go off and public awareness is raised, Brewster and Burgess have a race against time to apprehend the stalker. But danger comes not just from knives and bombs. Murder is deadlier when the heart is involved.