When Western intelligence services recognize a global jihadist attack has been mounted, the United States and the UK - its primary targets - lead the counter-offensive. Sally Hanning, a brilliant British MI5 agent whose parents were massacred in a terrorist ambush, is seconded to the CIA task force to hunt the Iranian mastermind through Al Qaeda's intricately coded use of social media and the Internet. Jack Irvine is NSA's guilt-burdened code-cracker - it was his diplomat-father's mistake that instigated the ambush in which Sally's parents died - who hacks his way into Iran's intelligence service. Attack after attack is foiled but the Al Qaeda mastermind eludes MI5 and the CIA every time. As they prepare to head off the final, ultimate attack, they realize, almost too late, that the plot is far more sinister than they had ever thought possible.