people were being offered indulgences for sale. >> narrator: leo x realizes not only would the sale of indulgences deepen the pockets of the catholic church, but it will also fund the expensive construction of st. peter's basilica. >> people go to st. peter's now and think about how did they get all of the money to build this. well, they were taxing people with indulgences. >> the whole thing about st. peter's indulgence is it was applicable to your dead relatives. so you could get your relatives out of purgatory by paying for indulgences. >> narrator: as word of the pope's campaign for indulgence sales spreads throughout europe, it triggers a reaction from a fundamentalist professor in germany. >> martin luther heard about this and found it obscene. >> narrator: martin luther, a