It was the first song he ever learned how to play, and the sharp tang of regret that it brought him every time was enough to keep him from strumming out the melody for a long time.
But as he stared at the little boy in the crib - his little boy - he had no choice but to pick up the guitar and play, his voice rough and hushed in the stillness of the room. Each word of the song tried to stick in his throat, bringing back memories of a childhood he'd rather leave far behind him.
He knew that there would be times when his job kept him from being a father. But he never wanted it to be like it had been for him and his dad. The missed chances and missed birthdays turning into a bitterness that bred a hateful silence and misunderstood pain.
He would know his son, dammit. And there wasn't anything in this galaxy or any other one that could keep him from that.
As the last note faded out, there was a quiet step behind him and then a gentle hand in his hair as Elizabeth leaned down to kiss the top of his head.
"You're so good with him," she whispered.
He leaned his head against her body and they watched their son sleep.