"The wind takes your skin-mask from your hands. Your twin screams and screams. The trees bend to whisper. 'Every week,' they say. 'Every week.'"
The Face-Tailor, whose real name is Benjamin Villein, figured out how Snuffers copy faces and turn them into masks. Understandably, the snuffers are a bit upset with him, and have persuaded the Constables to hunt him down. It is unknown whether or not he actually did something to deserve this; before all this happened, he was employed at the Ministry of Public Decency.
He recorded many hints and tips as to what he does in his Liber Visionis - Book of Faces.