As his route took him past Cell 426, he looked in to find the occupant still sitting curled on her narrow bed, her full concentration on the small blue book which seemed to be her favorite reading material. Just as she'd been the last five times he'd crossed in front of her cell.

"Good night, Doctor Song," he called out as he passed.

She looked up and smiled. "Good night,"she replied before turning her attention back to her book.

This pattern repeated, more or less the same, the next three times he came to her cell. On the fourth, however...

The cell was empty.

And he really, really, didn't want another one of those on his record.

Then he remembered the advice one of his older, more experienced colleagues had once given him after a particularly strong dressing-down by the prison's governor. So, instead of running to the alarm box, he stepped around the corner and waited two minutes before popping back round to her cell.

There she was, sitting curled on her bed once more. She might have been writing in the book this time instead of reading from it, but still, she was there, and that's what counted.

"Good night, Doctor Song," he said.

She looked up from her writing and answered, "Good night," in exactly the same tone she'd used every other time that night. Only her eyes, sparkling with controlled amusement, gave any indication that this time might, in fact, be different from all the others.

The guard continued on his route, relieved to have escaped another "situation". If he were honest, though, the strangest thing about Doctor River Song wasn't, in fact, how often she managed to escape. It was something else one of his older colleagues had pointed out to him. In all the years Doctor Song had been at the prison, not a single one of them had ever actually seen her sleep.