In the public hearing hall of the Mogang Notary Office, 372 people watched the city lord, Ji Bai, die in the Vaulted Pavilion. The murder weapon was a page of contract paper pressed against his chest. Its nineteen lines recorded grain deliveries and payments, and the signature matched the identification number of Sang Wujiu, a third-rank copyist in the Records Department: 1907. The verdict was already posted above the door: prove your innocence within thirty days, or your entire clan will be implicated and executed by strangulation. Pu Zhao held up the bloodstained contract and asked whether Sang would offer a defense. Kneeling on the blue bricks, his wrists marked purple by hemp rope, Sang Wujiu said, "The handwriting is mine. The paper isn't." He recited that the page contained nineteen lines and 521 characters, with three ink dots, each at the first character of a line. That was the rule for marking the start of a copied line and taking a breath; an outsider couldn't have copied it. But the number in the corner had been cut a fraction too short, leaving it flush with the watermark. The four digits were 1907. The Records Department had 141 copyists, numbered starting at 1700, and he was the last. Yet 1907 was also the paper number for the fifth batch of duplicate Celestial Contracts, which should have been destroyed three years ago. That batch had been burned in public. Thirty-four people watched the papers burn, and the ashes were then smashed into a vat of brine. Two old men holding teacups in the hall froze mid-sip. Sang Wujiu looked up at Pu Zhao. "Then where did this paper come from?"
