The TARDIS landed outside River's cell at Stormcage. The doors exploded open and a man in a classy black suit shot out.
"River! I'm sorry! The TARDIS wouldn't let me drive and I-"
He stopped as the sight before him registered. The door was open. The bed was untouched. Any sight that it had been lived in was absent.
He fought back tears as he entered.
She was gone. He was too late.
Something on the bed caught his eye. As he came closer, he recognized River's neat handwriting and snatched it up.
To my love,
I'm on an expedition. Don't know when I'll be back, but when I am I will find you.
I love you forever,
River
He sat down heavily. It was time. He looked at his watch.
May 25, 2108.
Some day in the future, after he'd taken her to the Singing Towers for the first...and last time, this would be the day he would have to set the TARDIS to to go give Amy and Rory the horrible news that their daughter would not be coming home from the Library.
Tears began to fall as the guilt filled his conscious. He pressed his face into her pillow, refusing to move. It smelled exactly like her and, with each breath, more memories of her filled his mind. He wept harder, curling into a ball and hugging her blanket to his chest.
"Oh, River. I am so sorry."