The children and Mrs. Grose return from church, and the Governess is rather confused by the easy acceptance of her disappearance.
The Governess tells Mrs. Grose that everything is out in the open between her and Miles.
She goes on to say that she had a conversation with Miss Jessel (stretching the truth just a wee bit) in which the dead woman told her of the torments she suffers, into which she wants to bring Flora.
The Governess tells Mrs. Grose that she's made up her mind to "everything" – that is, to write to her employer.
A part of this "everything" is that the Governess resolves to tell the children's uncle about Miles's expulsion from school. She's decided that he must have been expelled for wickedness, since he's not flawed in any other way.
Mrs. Grose really doesn't want the master to get involved in Miles's potential wrongdoing; she tells the Governess that she herself will handle the situation.
The Governess reminds her rather tactlessly that she can't write, to which she responds that she'll ask the town bailiff to write for her. However, both ladies don't want to air Bly's dirty laundry for a stranger – and so Mrs. Grose tearfully agrees to let the Governess write to the uncle.