London, 1608. Three years after the Gunpowder Treason, the King's enemies prepare to strike again. Daniel Pursglove is tasked by royal command with one final mission: he must infiltrate the Serpents - a secret group of Catholics plotting to kill the King - or risk his own execution. But other conspirators are circling, men who would blackmail Daniel for their own dark ends. In the Serpents' den, nothing is quite as it seems. And when Daniel spies a familiar face among their number, the game takes a dangerous turn. As plague returns to London, tensions reach breaking point. Can Daniel escape the web of treason in which he finds himself ensnared - or has his luck finally run out?