In Mitch's conversation with Charlotte at the beginning of ''The Sixth Tuesday'' what sets the tone?

The fact that it is Charlotte who greets Mitch at the door immediately sets the tone because it means that Morrie is no longer able to do so. Morrie's condition is worsening, something that becomes obvious when Charlotte notes that her husband is no longer able to eat, and which in turn, gives Mitch a feeling of uselessness...... believing that his visits aren't really helping his old professor. A new sense of hope quickly follows when Charlotte reaffirms that is is Mitch himself that gives Morrie a sense of purpose...... that preparing himself to teach the lesson helps keep him going.