The email from a foreign prince offering 20 million dollars looks like a joke, yet advance fee fraud takes in billions every year. This episode traces its lineage to the Spanish Prisoner letters of the late 18th century and the Letter from Jerusalem documented by Vidocq in the 1830s, then to Nigeria in the 1980s and 90s, where an oil price crash, youth unemployment, and cyber cafes produced the Yahoo Boys. The name comes from Section 419 of the Nigerian Criminal Code, though the senders may now sit in Amsterdam, Spain, South Africa, or Jamaica.

The central insight comes from Microsoft researcher Cormac Herley: the bad grammar is a filter. Sending ten million emails costs nothing, but grooming a reply takes hours, so absurd messages repel skeptics and leave only the most susceptible. From there the episode follows the money through Western Union and cryptocurrency mixers, the invented fees that trigger the sunk cost fallacy, and the newer bait of puppies, romance, jobs, and phone towers. It ends with the people who embezzled, were kidnapped, or were killed.

• Scammers abused the Telecommunications Relay Service for deaf callers, whose operators were legally bound to read fraudulent scripts verbatim without warning the victim.
• In the fake check scam, a victim deposits a forged cashier’s check for 5,000 dollars, wires 4,000 onward, and is left liable when the bank reverses the deposit.
• The FBI reported more than 3.5 billion dollars in losses to advance fee and romance scams in a single year, and a UK report put the average victim’s loss around 31,000 pounds.
• A former county treasurer in Michigan embezzled public funds to keep paying fees and was sentenced to between nine and 14 years in prison.
• Jette Jacobs, a 67 year old Australian who had sent more than 90,000 dollars to a supposed fiance, was found dead two days after arriving in South Africa in 2013.