They’re called “zombie” mortgages: old second loans from the subprime era that many homeowners had good reason to believe were canceled or forgotten. Now, years later, debt collectors are coming after the money. And they’re ready to foreclose if people can’t pay. It sounds like a horror story, but a new Bloomberg investigation has found that it’s a terrifying reality — and hundreds of thousands of homeowners could be at risk.

On today’s Big Take podcast host Sarah Holder and Bloomberg data journalist Noah Buhayar look at what a trove of records from one debt collection company tells us about how the industry operates as a whole and why cashing in on dormant mortgages has become big business.

Read more: How Debt Collectors Spin Riches from Zombie Loans