It's the week before Christmas when a lone robber bursts into a busy Glasgow post office carrying an AK-47. An elderly man suddenly hands his young grandson to a stranger and wordlessly helps the gunman fill bags with cash, then carries them to the door. He opens the door and bows his head; the robber fires off the AK-47, tearing the grandfather in two. DS Alex Morrow arrives on the scene and finds that the alarm system had been disabled before...