John Oliver and his team decided to look into the phenomenon of televangelism, and just how much money many of these preachers are making. 

In their investigations, they uncovered the lavish lives of the preachers who have private jets, huge mansions and personal fortunes as a result of targeting vulnerable people who do have religious faith. 

In particular, Oliver looks at what is called "seed funding", where the televangelists promise that the more money you "sew" (by sending it to them), the more you get back. In order to test this, Oliver got in touch with a preacher and engaged in the back and forth correspondence for months that involved him handing over a lot of money. 

In order to test exactly why it was so easy to get away with all this, Oliver set up his own church called Our Lady of Perpetual Exemption, and plans to push the limits to see if the IRS will step in and put a stop to it.