Evening Walk

Jeff was in the park, walking his dog as he did every night before throwing in the towel and going to bed.
Two people he had never seen before were walking towards him. One was a boy of around 14 and the other was an older woman, most likely his grandma. As they drew nearer Jeff noticed something strange about the woman. It was her left arm. She seemed to be holding it at a very unnatural angle. The hand was darker than the one which hung by her side and Jeff realised it was a prosthetic. He tried not to stare, but couldn't help it.
"Lovely evening," Jeff said.
"Yes," replied the woman seemingly annoyed that they didn't have the park to themselves.
The two headed for the children's play area as Jeff headed across the grass towards the trees.
He saw them both sit on a seesaw. They bounced up and down for several minutes without a word. Neither seemed to be enjoying themselves in the least.
Jeff watched from beneath a tree as the boy climbed off and then helped the woman stand up. They both walked back the way they had come in silence.