Rome's Executioner (Vespasian, #2)

Thracia, AD30: Even after four years military service at the edge of the Roman world, Vespasian can't escape the tumultuous politics of an Empire on the brink of disintegration. His patrons in Rome have charged him with the clandestine extraction of an old enemy from a fortress on the banks of the Danube before it falls to the Roman legion besieging it. Vespasian's mission is the key move in a deadly struggle for the right to rule the Roman Empire. The man he has been ordered to seize could be the witness that will destroy Sejanus, commander of the Praetorian Guard and ruler of the Empire in all but name. Before he completes his mission, Vespasian will face ambush in snowbound mountains, pirates on the high seas, and Sejanus's spies all around him. But by far the greatest danger lies at the rotten heart of the Empire, at the nightmarish court of Tiberius, Emperor of Rome and debauched, paranoid madman.