A Saturday evening in London in autumn and Detective Inspector John Carlyle is out jogging up the Mall towards Buckingham Palace. On Constitution Hill he comes across a young girl aged around nine years, alone and shoeless. He approaches her and identifies himself and realises she does not speak English. He contacts the police station and despite a well dressed man trying to claim her, he takes her to the station. She is taken into care by Social Services, but someone impersonating the police take the girl away.

Carlyle and Sergeant Joe Szyszkowski are determined to find the girl. Something the girl had said convinces Carlyle that someone connected to Buckingham Palace is involved. He talks with SO14 the Royal Protection Unit, but as he left them a few years ago under a cloud, he doesn't get anywhere. He decides to talk with a policewoman who works for SO14 but only succeeds in getting her attacked. He has more success with a detective superintendent in Vice who introduces him to a Ukranian called Ihor Chepoyak and through him a high class call girl called Olga. Carlyle, despite being warned off, is convinced that a mystery suicide by a policeman from SO14 is integral to this investigation. Unknown to him there is a parallel investigation into child protection and the two investigations will come together.