At the very end of act two, Giles and Danforth come to the Proctor household with some very dire news--both of their wives have been arrested for witchcraft, and taken to the jails. They come just as Elizabeth, John's wife, is in the process of also being arrested. Francis and Giles know that their wives are innocent, are desperate to try all that they can to get them out of jail. Both of their wives are very old, and going to jail will be a great burden and trial on their health. Giles's wife, Martha, was arrested because she told a man named Walcott that if he didn't start feeding his pigs, they'd all die; well, he didn't feed them and sure enough, they died. So, they arrest her on suspicion that her words cursed his pigs. If there is a more ridiculous reason to be arrested, I don't know what it is, and Giles himself feels the injustice and horror of it all. He wants to go talk to Danforth, and try to talk some sense into the guy, hoping that he will release his wife. Francis's wife was arrested "for the supernatural murder of Goody Putnam's babies." Somehow, the courts think that the kind, pious Rebecca Nurse cursed Goody Putnam's babies, making them all die at birth. Francis wants to talk to Danforth and convince him that his wife is innocent.
So, at the beginning of act three, all three men (John, Francis, Giles) go to the courts, armed for argument and battle, in order to try to get their wives exhonerated and released from the jails. As the act progresses, you will see how each of their attempts fail, and how in the end, the courts, in all of their illogical rationale, win that battle. I hope that those thoughts helped; good luck!