River: There has to be another way. Use the TARDIS. Use something! Save her, yes, but for God's sake, be sensible! [River tries to slap the Doctor, but he catches her wrist] How are you even doing that? I'm not really here.
The Doctor: You're always here to me. And I always listen. And I can always see you.
River: Then why didn't you speak to me?
The Doctor: Because I thought it would hurt too much.
River: I believe I could have coped.
The Doctor: No, I thought it would hurt me. And I was right [He kisses her passionately] Since no one in this room can see you, God knows how that looked.
[Vastra, Jenny and Strax look awkwardly at each other]
The Doctor: There is a time to live and a time to sleep. You are an echo, River, like Clara, like all of us in the end. My fault, I know. But you should have faded by now.
River: It's hard to leave when you haven't said goodbye.
The Doctor: Then tell me, because I don't know – how do I say it?
River: There's only one way I'd accept. If you ever loved me, say it like you're going to come back.
The Doctor: Well then. See you around, Professor River Song.
River: Till the next time, Doctor.
The Doctor: Don't wait up.