How a brutal assault led a woman to one of the CIA's most valuable Russian spies

On a warm day in late September nearly 10 years ago, Lisa Sales was in the basement of her Virginia home, going through files belonging to her former tenant, a man who had just been arrested and would later plead guilty to assaulting her.

Sales, then in her early 40s, picked up a flash drive in a small glass dish where she kept odds and ends by the printer. She assumed, she later recounted, that it was hers and inserted it into her computer. Instead, she realized the flash drive belonged to her former tenant, and it contained an investment report listing total assets of more than $16 million, a seemingly inexplicable sum for someone who had been paying $2,000 a month to rent a basement room in her house.