The first time he holds her she's tiny and pink and just wrinkled enough to be cute. She's not crying like all the babies he's read about in "What To Expect When You're Expecting" and "A Month By Month Guide To Your Pregnancy", she's just calmly staring at him, using all her energy to keep those cerulean orbs, the exact same shade as his own, wide open.
For a brief moment the hospital room fades into the background and it's him and her; and she's so tiny and so perfect and so utterly, utterly his. In that moment he knows, without a single doubt, that the squirming, red headed infant in his arms will be the centre of his universe and that he would lay down his life in a heartbeat to spare her.
Too soon the beeping, whirring cacophony of the hospital invades his consciousness and yet his eyes never stray from her, she's his personal magnetic north.
She's five when she first breaks a bone; he gets the call whilst at home working on his next novel, the kindergarten teacher sounds as panicky as he feels. Needless to say he's out the door and en route to the hospital before the phone has time to settle in its cradle.
The first thing he wants to do when he reaches the emergency room is see his daughter, to hold her as tight as he can and make all the pain disappear, but her teacher is preoccupied with explaining how the injury occurred; apparently Alexis was on the monkey bars when one of the boys decided it was his turn and tried to swing over her, resulting in both of them hurtling to the ground below. Castle's amazingly proud when he's told that Alexis first checked the boy was alright and then walked over to Ms Rosenberg and calmly informed her that she had an 'owie' and that she probably needed to go 'lopital'.
She's almost serene when he sees her, sat on the side of a hospital bed with a bright purple cast on her right arm, her skirt a little dirty and her hair starting to fall out of its French braid; purple is her current favourite colour she explains, because Barney the dinosaur is purple.
Once again she's not crying she's just staring at him with those blue eyes which hold both childlike innocence and wisdom far beyond her years. He promises himself then that come hell or high water he'll never let anyone hurt her again.