I lost the thread around the fourth equation.”

For the first time Zachary laughed in his father’s presence.

“So did half the room.”

It was a small, startling sound.

Brian smiled, then seemed to remember that a smile was not permission for more.

He thanked us and left with Eleanor.

On the ride home Zachary sat quietly until we turned into our neighborhood.

“I don’t hate him,” he said suddenly.