Some of the deals Siegel made were hugely profitable, while others proved more troublesome. As he soon discovered, after creditors sell off unpaid debts, those debts enter a financial netherworld where strange things can happen. A gamut of players — including debt buyers, collectors, brokers, street hustlers and criminals — all work together, and against one another, to recoup every penny on every dollar. In this often-lawless marketplace, large portfolios of debt — usually in the form of spreadsheets holding debtors’ names, contact information and balances — are bought, sold and sometimes simply stolen.