“Whenever your mom and you let me.” Leo studied him for a long, judging moment.

“That’s not a promise,” he said.

“No,” Alex agreed.

“It’s the only thing I can prove.”

That exchange, between a grown man and a five-year-old, contained more wisdom than Alex had encountered in years of adult life, and it reorganized his entire understanding of how he was going to have to earn his way back.

Because Leo, at five, had already grasped a truth that most adults spend their whole lives avoiding: that promises are worthless from a person who has broken them before, and that the only currency that means anything, from such a person, is proof.

Leo did not want to hear that Alex loved him, or was sorry, or would never leave again.