Disclaimer: I don't own Castle and never will. No copyright infringement intended.
The only thought running through Rick Castle's head right now is that "Kate has to be okay". She's the only thing he can think about he rushes up to the apartment building. He doesn't know what he'll do once he'll get inside.
What is he supposed to tell Alexis and his mother? Esposito and Ryan? Rick doesn't know what to do for the first time in a long time.
What if Kate's dying or dead already? (Don't think about that, a voice in his head whispers.) He can't lose her ever.
Rick Castle really doesn't know what to do next.