In The Crucible, Reverend Hale says, "Mary -- you charge a cold and cruel murder on Abigail." What does he mean?
In this scene, Mary has just told everyone in the house that the poppet they found there was indeed hers, and that she sewed it in court that day. She adds, "I-I believe I did, sir" when asked if she was the one to put the needle in it. Even better, she says, "Ask Abby, Abby sat beside me when I made it." So, if this is true, and Abby saw her put the needle in the poppet's belly, then that means that Abby stabbed a needle into her own belly, and then accused Elizabeth Proctor of doing it, through her spirit as a witch. That means that Abby was plotting Elizabeth's murder. Which she indeed was; Elizabeth already suspected it. Earlier in that act Elizabeth had stated ominously and incitefully, "She wants me dead, John, you know it!" Unfortunately, no one but John (and Elizabeth) really believes that Abby is capable of such malicious intents, and Elizabeth is wisked away to jail, all because Abby was an opportunistic plotter who schemed to get here there.
When Mr. Hale tells Mary Warren, the Proctors' servant, that she charges "a cold and cruel murder on Abigail," he means that, according to what Mary has just told everyone, Abigail is guilty of attempted murder. Abigail herself did not physically commit a murder, but if she truly saw Mary stick the needle in the poppet's belly and then claimed that Elizabeth Proctor's specter pushed it into Abigail's own belly, this would constitute evidence enough to convict Elizabeth of witchcraft—a conviction that would result in her hanging. Therefore, Abigail would be guilty of giving false testimony that results in Elizabeth's death, a charge tantamount to murder. Mary is terrified of Abigail and tries to back down once she realizes where the line of questions has led her, but it is to no avail, especially after Elizabeth is arrested and carted away in chains. John Proctor will force her to go to the court and testify against Abigail in Act Three.