She knew too much, the first time he met her. But who's willing to die for you when they don't even know you? Friendship is a funny thing when one person knows more than the other, when the timelines aren't synched.
He's always wondered why it had to be a bowtie, why that was the thing that caught his eye in the hospital closet in Leadworth, like it had been placed there with a "Take me, Doctor" sign on it. He's always wondered. Until now.
He holds out one end to her, and she takes it. This is the last day he will wonder who he is to her, who she is to him. He will come for her the day before she dies, and they will watch the stars together. Will it be him, or will it be another him? It won't matter. She will know all his faces.
Now he knows why she died for him. After all, if you've halted time for someone, dying must not be such a big thing.
As he winds the cloth around his hand, he knows. The first moments of marriage are the last moments of an upside-down friendship. This is the kiss that will turn it all rightside-up.