His Second Heart

There was one room in the TARDIS that was always locked. Clara couldn't help but be curious about what lay behind the TARDIS-blue door; it was the only such coloured door on the entire ship. The handle was golden, as was the Circular Gallifreyan and the running wolf that adorned the blue wood. One day, Clara grew frustrated of the Doctor's evasion. Every time she asked about the door, he would distract her with a trip somewhere. So Clara enlisted the help of the TARDIS.

The TARDIS was more than happy to unlock the door for her Impossible One. She needed to see the Doctor's second heart, the one he had lost so many years ago.

Whatever Clara had expected to see, it wasn't a messy bedroom, with pink walls, an unmade bed, clothes scattered about, and a desk cluttered with pictures and souvenirs from various alien planets. Clara went over to the desk and looked at the pictures.

All the pictures had something in common: a beautiful blonde woman with large hazel eyes. She was with both of the Doctor's ninth and tenth incarnations, which Clara recognized from when she had entered his timeline. She wouldn't have thought the girl was anything other than yet another former companion, were it not for the look on the Doctor's face when he looked at her, like she was his whole world.

"Her name was Rose," a Scottish voice said from the doorway. "Rose Tyler." The Doctor stepped further into the room and seated himself gently on the bed. "Found her in the basement of Henrick's, about to be killed by some Autons. I grabbed her hand and told her to run, and we never stopped." When Clara looked at the Doctor, she was stunned to see every single one of his years visible in his gaze. He looked old and tired, but at the sight of the picture in her hand, he smiled and something flickered in the depths of his eyes. "Would you like me to tell you about her?"

In the hours that followed, Clara learned an absolute truth. No matter how many years passed, no matter how many times he regenerated, the Doctor would never get back his hearts.

The universe revolved around the Doctor, but the Doctor revolved around Rose Tyler.