Los Angeles-based investigative journalist Mariana van Zeller has spent much of her career talking her way into black markets and sitting down with the people who run them. For her latest assignment, the Portuguese-American reporter created a fake dating profile and waited for scammers to come looking for her.

Van Zeller donned a wig and a prosthetic nose, then introduced the internet to Mary Zell, a divorced woman in her 50s looking for love to better understand how people fall victim to romance scams.

She soon had plenty of admirers. Men claiming to be George Clooney and other celebrities began courting her. One persistent scammer posed as a four-star general stationed in Syria. He sent flowers, talked with her for months, and eventually sent videos teaching her how to use a Bitcoin ATM.

Van Zeller then worked with a hacker to find the man behind the messages.…