Derek had never been quite the model father — Always a bit too engrossed in his work, rather staying overtime at the hospital than come home and have dinner with you. He knew it was wrong, hell, he saw it firsthand with Meredith what it did to a person, but he couldn’t quite bring himself to change. Until that one evening.

Derek was just stuck in a complex surgery — His hands quite literally stuck in a patiens brain when Doctor Bailey came in, stonefaced as always and told him that there was a case of a teen with alcohol poisoning in the ER. Derek didn’t know, why he was needed — Frankly, he was quite pissed his important surgery was interrupted for that. He couldn't have known, could he? He couldn't have known that it was you, his precious daughter, who was in the ER.