For almost three years starting in the fall of 2015, a 56-year-old Chinese-American tour guide named Xueha "Edward" Peng would periodically carry out a strange errand: Every few months, he'd book a room at a certain designated hotel—first in California and later in Georgia—and leave $10,000 or $20,000 in cash in the room, inside a dresser drawer or taped to the bottom of a desk or TV stand.

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