When an Auditor knocks on Liam's door, he thinks she's there to kill him. Instead, he's offered the chance to correct a basic facet of reality.
The Pythagorean Theorem is wrong. Or at least, that's what the AIs say.
Artificial intelligence lies all the time. It's often not malicious. In fact, AIs usually lie to please their users. But what's to stop these lies from being considered truth? The Audit. If an AI lies, but a user is unsure about it, they consult The Audit, and the truth is found. But if something so fundamental to our understanding of the universe is wrong, what is the truth? What is reality? Auditor Liam must unravel this mystery before reality itself unravels. And that's all before masked zealots try to kill him.