Tark smiled in that slightly patronizing way that makes you feel dumber than the average pocket calculator. "It’s Latin, Wolf. It means ‘Who will guard the guards themselves?’ Juvenal asked this question in his Satires , but it applies here. Harry doesn’t like striking a deal with an outside group to clean his own house. By the same token, he doesn’t figure he has a whole lot of choice, which is why he wants to be in on the bust of the bad cops. He reminded me that those who have so little need their honor, and he needs the bust."