A spy alone. An enemy within. A veteran American spymaster weaving an elaborate web. A politician who makes a high-stakes promise he can’t keep. A clutch of sophisticated air defence missiles stolen in Ukraine. A terrorist cell with plans to commit an outrage in the US capital. And, at the centre of it all, a British agent, operating alone and undercover, on a desperate, globe-trotting mission to prevent catastrophe. She cannot fail...