For three years I had feared that grief and worry had broken something in my son, had stolen his childhood and left an anxious little adult in its place.

But watching him ride, light and laughing, finally free of the invisible mountain he had been climbing all alone, I understood that nothing in him had been broken at all.

Mark had not only left us memories when he died.

He had passed something down to his son, straight into his blood: his courage, his fierce stubborn loyalty, his unbreakable heart.

I had spent three years afraid that losing his father so young would leave a wound in Caleb that never closed, would deform his childhood, would take from him some essential lightness he could never get back.