It is the run-up to Christmas when two seven-year-old boys are abducted from the streets of Glasgow. For DI Colin Anderson the case is especially disturbing, because the boys look so much like his own young son Peter. When a simple house fire turns into a full-scale murder investigation, and with cold and flu season having taken many officers off the street, the force is stretched to breaking point. DS Costello's hunch is the crimes are connected, and a killer is ingeniously hiding his trail. As the squad continues to struggle working both cases, for DI Anderson the nightmare is about to get terrifyingly close to home.