Holly Black. Red glove (№ 344279)

For proper setup you need to find someone who can easily pass for the villain. Best of all, if he has done something bad, and quite good, if really at fault.
Then the conscience will not torture.
The story must be believable. Simple lies everyone will believe. In a simple lie people believe much more readily than the truth. The truth is often confusing, rude, unpleasant. But how can I to judge? Let them believe a plausible lie.