When a passenger jet crashes in Denver, Colorado, nobody survives. In Glasgow, Alex Cahill gets a call from the wife of a former US Secret Service colleague - a man supposedly travelling on the doomed plane. However, there's no record of his name on the passenger list. And Cahill's connections in the US intelligence agencies are unforthcoming. Desperate to uncover the truth behind the disappearance of his old friend, Cahill and Logan Finch head to Denver to confront the FBI. Meanwhile, a perfect storm of events gathers across the globe, from Colorado, to war-torn Afghanistan and to the mean streets of Glasgow - where DC Rebecca Irvine is investigating a new drug that is killing users. It is a deadly storm that will engulf them all.