Red. Come to my apartment. Please." Joe races over, worried. He's seen Caitlin several times since her last SOS, and she's been doing well. He wonders what could have set her off. When he gets to her door, she opens it with a flourish and nearly knocks him off his feet with the vehemence of her hug.

"Happy birthday, Joe," she says from against his shoulder. "I know Barry and Iris have a party planned for later, but I wanted to see you first."

She pulls back, and Joe shakes his head. "You nearly gave me a heart attack with that text message."

Caitlin smiles sheepishly. "Sorry, but I wanted to surprise you." She hands him a wrapped package, and he opens it. All it contains is a pink, flowered journal. He looks over at the girl, confused.

"It's, um—every time you've taken care of me or texted to check on me, I've written you a letter. I wasn't going to show them to you. The first few aren't very nice. But I realized it was only right to give them to you, since I'm not very good at saying out loud how I feel about things."

Joe feels his eyes mist. "I'll only keep this until tonight. Then I'll give it back so you can keep writing. Journey's just beginning, you know."

"I know," she answers, coming willingly into the arms he opens for her.

This time, he holds her against him, and he says, "Caitlin, I'd be very proud if you were my daughter."

She pulls back for a second and says playfully, "Detective West, I thought I already was." She hugs him again, and it's as simple as that.