In Act III, when John Proctor brings Mary Warren to the court, he is assisted by Francis Nurse and Giles Corey, both who have brought their own pieces of evidence to try and indicate that what is happening is wrong and should be stopped. Giles Corey brings a deposition that accuses Thomas Putnam of deliberately profiting from the witch trials, as he is one of the largest landowners in Salem and is able to buy the land that is taken from those who are accused and hung as witches. Note what Corey says:
If Jacobs hangs for a witch he forfeit up his property--that's law! And there is none but Putnam with the coin to buy so great a piece. This man is killing his neighbours for their land!
Putnam therefore gets his daughter to accuse his neighbours of witchery so that he is able to then subsequently buy their land when they are hung for witches. This is what Corey accuses Putnam of in Act III.