A large country mansion. A locked room. A gruesome murder.
Russian oligarch Alexander Volkov has invited 1000 guests to a party at his palatial Surrey residence, Westgrave Hall. But while giving a private tour of the library, a gunman kills Volkov, wounding his ex-wife and slaying her new beau. Nothing makes sense to DCI Craig Gillard. In the blood splattered crime scene there are no forensic traces of anyone else involved, CCTV shows no one entered or left the library, and everyone seems to have an alibi.