Charismatic Edward van der Linden runs Eleventh Hour, a massive global enterprise committed to solving the world's environmental problems. The company is funded exclusively by super-rich philanthropists, who use its influence for their personal crusades, making it an exclusive, powerful and highly secretive club.

Detective Chief Inspector John Cavey, the Met's most successful murder detective, is investigating a rash of killings amongst London's homeless community that is looking less like a serial killing and more like mass extermination by the day.

Twenty-six-year-old Caroline Hartley joins the Eleventh Hour corporation as Edward van der Linden's speech writer, but it isn't long before she starts to suspect that everything is not as it seems at the company, as she accompanies her new boss to the world's environmental hotspots. Caroline learns that Eleventh Hour is conducting ground-breaking medical research in a laboratory deep in the jungles of Guyana and starts to question the company's benevolence. As she struggles to thwart Edward van der Linden's deadly intentions, her mission cuts across DCI Cavey's murder investigation, which has drawn him to the doors of the mighty Eleventh Hour corporation, where both of them discover the significance of 'the rule of 72'.