Act IV:Why has Hale returned? How and why has he changed?How and why does Giles die? Why wasn't he hanged?
Hale has returned in an attempt to fix what he helped cause. On his arrival into town, he seemed boastful of his ability to take care of the situation. As the panic and hysteria grew to new heights, Hale has realized that innocent people are dying, and justice is not being served. He attempts to get those imprisoned to lie and "confess" to save their lives, and he has attempted to get the court to postpone any further executions, but he is having no luck.
Giles Corey is not hanged. He is pressed to death using heavy stones. He was given this sentence because he went to court and accused Putnam of getting the girls to accuse people he had issues with, and those who he could profit from their imprisonment. When he refused to name his source for information, he was jailed for contempt of court. He was pressed to death to get a confession from him, and if he confessed, he would have been hanged. In historical transcripts, they say the last words he ever said was "more weight".
Having realized the consequences of his actions and that justice is not truly being exacted when people are being executed for crimes they did not commit, Hale returns to make things right. In his attempt to course correct his own errors, Hale works to convince those charged with witchcraft to falsely confess in order to avoid execution.
Giles Corey, who is one of the individuals charged with witchcraft, dies after being pressed with stones in order to exact a confession. This torture attempt did not work and resulted in his death because Corey refused to confess. Corey had initially been imprisoned after he would not provide the court with the name of his informant regarding his accusations against Thomas Putnam. Corey does not hang because he dies during the confession extraction process rather than actually being convicted and executed.