Disclaimer: I in no way claim ownership to any part of the Doctor Who franchise. This was merely a plot bunny that wouldn't leave me alone.

The Doctor and his wife were in her classroom at the university, flirting as usual. There was occasionally annoying the other, too, but that was mostly on his part. The unusually peaceful moment between the two was broken by four booming, impatient knocks on her door.

With a roll of her eyes, River stood up from her seat on top of her desk and smiled apologetically back at the Doctor. She opened the door and quickly slipped through, the door closing behind her with a click. The room was left in tense silence with the Doctor looking at the door, eagerly awaiting River's return. With the universe thinking that River killed the Doctor, they'd both agreed that when he came over to see her, no one could see him. Though necessary in case the Silence found out, the Doctor wished he could go out and see who was out there, instead of waiting for River to come back in.

He tried to be patient, but you couldn't put "the Doctor" and "patient" in the same sentence. That was the beauty of having a time machine, after all. You could just cheat and skip ahead. After a few minutes, he started pacing to get his restless limbs moving again. Finally, after what seemed like hours to the Doctor (but more likely only 30 minutes), River returned with the Doctor's favorite smile on her face. It was the one she always had on when they were in the middle of an adventure or there was a mystery afoot.

"Who was it?" he asked.

"It was a man named Mr. Lux. Apparently he and a team are going to investigate the Library in a month and he wants me to lead them. I accepted, and we're going to see each other next week so he can tell me more. Oh Sweetie, this is a case I've been dying to solve for years!" she beamed before kissing him on the cheek.

He will knock four times and your Song will end. For centuries, he'd thought that it had meant that his tenth incarnation's life was ending, but now he realized how wrong he was.

With a sigh and a fake smile, the Doctor asked, "Hey, River, why don't we celebrate by going to see the Singing Towers of Darillium?"