In Thank You, M'am by Langston Hughes, the reader might expect Mrs. Luella Bates Washington Jones to drag Roger to the police station as she has just stopped him from stealing her purse. Mrs. Jones is clearly a down-to earth woman, and whilst holding his shirt with no intention of letting him get away, she tells him plainly that if he did not want her to react, he shouldn't have bothered her in the first place. Now that he has, Mrs. Jones intends to teach him a lesson by showing him what it means to respect someone and trust him to do the right thing. Expectations often govern people's reactions and Mrs. Jones's assertions that he will remember her, have Roger worried about what she intends to do, having dragged him up the street and into her house.
Mrs. Jones insists that Roger wash his face and she makes them some food. While she is busy, she leaves her purse and doesn't even watch Roger to ensure that he doesn't still steal her purse and run away. Roger however is unsure of the situation which is why he says that "he did not trust the woman not to trust him." He is confused and his words reveal that when he uses a double negative, effectively reversing the negative. In the first place, when he says that he does not trust her what he means is that he knows that he has not yet done anything to earn her trust so he cannot rely on her trusting him. In the second instance, he has seen enough of her to understand that she has respect for him but he is still unsure of the situation. He would like to think that she trusts him but he does not believe it could be possible.