Who'd try to con the most notorious gangster of the 20th century?
'Count' Victor Lustig.
Lustig became infamous for selling the Eiffel Tower, twice. But his most daring con was aimed at none other than Al Capone.
He told Capone he would take $50,000 and double it in 60 days. Lustig appeared in front of Capone 60 days later.
"Mr Capone, I've failed. I thought I'd manage it; Lord knows I need the money too, but... no dice."
It should've been curtains for our friend, The Count. But he reached into his pocket and gave back every cent of Capone's money.
Now Capone was confused. He had expected $100K or nothing but ... his money back? What a shock! As Lustig was leaving, Capone responded - "I knew you were a conman, but I never expected this! If you're going through it, here's $5K to tide you over."
The Count accepted, leaving with his tail between his legs.
He'd just conned Capone.
He never planned to double the money. The Count deposited the $50K in a bank and left it there.
During Capone's time as a gangster, he'd grown wary of everyone around him, expecting to be betrayed at every turn. The Count used this to his advantage.
The reciprocity bias.
When you receive a gift, you want to respond in kind. The Count had been "honest" with Capone, giving him back his initial money, so Capone responded in kind, by helping out The Count.
That was his plan all along.