The Left Hand of Calvus — L.A. Witt

Former gladiator Saevius is certain fortune's smiling on him when a Pompeiian politician buys him to be his bodyguard. But then his new master, Laurea Calvus, orders Saevius to discover the gladiator with whom his wife is having an affair. In order to do that, Saevius must return to the arena, training alongside the very men on whom he's spying. Worse, he's now under the command of Drusus, a notoriously cruel -- and yet strangely intriguing -- lanista.

But Saevius's ruse is the least of his worries. There's more to the affair than a wife humiliating her prominent husband, and now Saevius is part of a dangerous game between dangerous men. He isn't the only gladiator out to expose the Lady Verina's transgressions, and her husband wants more than just the guilty man's name.

When Saevius learns the truth about the affair, he's left with no choice but to betray one of his masters: one he's come to fear, one he's come to respect, and both of whom could have him killed without repercussion. For the first time in his life, the most dangerous place for this gladiator isn't the arena.