Here's the scenario. A businessman arrives in a foreign city - let's say Istanbul - for a conference. He gets there a day early to do some sightseeing. He heads down to Istikal, the main drag, and a guy approaches him.
He's Turkish, but also from out of town. And because the two are both alone, he suggests going for a beverage. The local man buys the first couple of rounds, talks about the local scene. Then he suggests going somewhere else. There, they meet a woman and the second man suggests getting drinks for her. After a couple of rounds, it's time to call it a night. The bill comes and it's a staggering €800 (Dh3,747) for six drinks.
Our businessman complains, but a massive guy turns up. His new friend is embarrassed. He suggests splitting the bill and getting out of there. Both their credit cards are charged. The second man apologies profusely and says it's best to call it a night, so they both leave.
What our businessman will not know is that his new friend's credit card wasn't charged and after he heads off, he doubles back to the bar to collect his share of the €400 our businessman just handed over. Our man has just been scammed.
In his new TV series Scam City for the National Geographic channel, the economist and author Conor Woodman travels to 10 of the world's great metropolises to uncover the scams that hit tourists and business travellers.
"There is the taxi scam in almost every city," Mr Woodman says. "The driver taking you the long way to your hotel from the airport is pretty much universal. But some [scams] are unique to particular places."
In Buenos Aires, for example, counterfeit money is a huge problem and anyone who arrives in the city is likely to be handed fake notes at some point during their stay.
In Barcelona, Mr Woodman found that pickpocketing was common because of the light punishment for petty crime.
"There is a real cultural aspect to scams," he says. "In Barcelona, people are quite light-fingered and that's a function of the law in Spain. In Marrakesh, the law is very hard on petty thievery so the scams that I encountered … tended to be less about violence, extortion and just plain thievery; they tended to be slightly cleverer with more confidence scams or scams based on deceit."
An example in Marrakesh is the carpet vendors who fade new and cheap factory-made carpets in the sun for a fortnight, then sell them at vastly inflated prices as antiques.
The con artists there "like to encourage you to part with your money and it's more fool you if you do," the presenter says. "That puts a lot of responsibility on you then as a traveller to do your homework. You are still a victim, but a victim of your own greed, perhaps, and naivety."
Rather remarkably, Mr Woodman manages to win the tricksters' trust and gets them to explain how and why they got into this line of work.
"Most of them are career criminals," he says.
"They are known to the police and not worried about giving themselves away. They are very professional and very skilled at what they do, but they operate in the shadows. What I gave them was the opportunity to step out of the shadows and show their extrovert characters. I encouraged them to show me how good they are at what they do."
Fraternising with criminals did, however, result in some hairy moments, most notably with the counterfeiters in Buenos Aires. To do an interview, Mr Woodman was asked to leave his security team behind, then given directions to an unnamed location. The gang wore horror masks and snorted cocaine throughout the meeting, which took place in a locked room.
"They were all armed. One had a pump-action machine gun and they were all really agitated," he recalls. "Those guys kill people every day. When they are not doing counterfeit money, they are doing armed robberies and kidnap. They are seriously heavy dudes."
The one thing that Mr Woodman wasn't able to figure out was how much all this crime costs.
"I don't think anyone really knows the size of it or can put a number on it," he says. "Travellers under-report these scams. Once a city becomes lawless, of course, it's a problem.
"But these are the world's greatest cities, functioning cities, with huge tourist industries. Petty crime in every one of them is absolutely rife. It's not destabilising as such; it's more like a parallel economy running beside the real economy."
Scam City airs on the National Geographic channel