He followed the murmur to a narrow square where a pale tent had been raised overnight. A sign nailed to a leaning post declared, in uneven ink: THE EXCHANGE. Inside the tent, a woman sat on a low stool, watching a line that threaded out past the lantern seller and around the spice barrels. People came forward carrying small, curious things—buttons, bottles of rainwater from special storms, a child's single-button shoe—and left with pockets lighter or heavier depending on the trade.