A/N: Hey there random person! This is one of the many library fix-its out there but its just how I think it could have possibly worked... Currently it is just a one shot but maybe I will use it in something else. Or maybe I won't...
Well whatever happens, I at least hope that you enjoy this :D
The Doctors wife was many things but one thing she wasn't was stupid. In fact, she was really quite clever; clever enough to know that one day the Doctor wouldn't be able to save her. But that didn't mean the she couldn't save herself.
It was all quite simple really. Their timelines were back to front and as she got older the Doctor got younger. He knew her less and less till he was running out of firsts and she was running out of lasts. But the biggest clue was the sadness in his eyes. Sometimes when he looked at her she could see it just under the surface and it broke her heart.
The Screwdriver had been another clue and the crying at Darillium had made it outright obvious that her cards were finally up. The Library would be her grave.
But River Song was a Pond and she was not going to go down without a fight. She was also the wife of the Doctor and like her husband she could bend rules with the best of them. In this particular case it was the Laws of Time, even if they were intrinsically linked to the fabric of the universe. And most importantly she was the child of the TARDIS and beholden to all manner of spoilers she should never have known, such as the exact nature of her supposed death.
Her wedding day had been a rather useful, practical lesson on how to circumnavigate fixed points. Her husband had only needed to fool people into thinking he was dead, and River only had to prove to him that she was dead for this particular point to stay fixed.
So then all it came down to was preparation and acting, and what was acting but theatrical lying? And River Song was well acquainted with lying.
The Doctor was her audience and while his tenth incarnation lay unconscious and handcuffed it gave her just enough time to wire the spare set of fission cells into the computer. What spare set of fission cells? Why the very ones she had planted in the library back when it was still being built thanks to her vortex manipulator and a black market trader by the name of Glitz.
She then hooked it up to the countdown and set up for her shows finale. It didn't take much longer for her Sweetie to come around and look at her with those sad, sad, young, old eyes. He begged her to stop, for it to be him. It broke her heart but she was well practiced at never letting him see the damage. Instead, she insured the correct spoilers were revealed so that he would do as he had already done, not changing a single second of what had been, and thusly the infinite loop of a self-fulfilling paradox was created.
Then as the countdown hit zero, the room lit up with an impossibly bright light; her cue to quickly activate her short range teleport to her ship waiting patiently in orbit.
The young, spikey haired Doctor believed he saved what was left of River Song. That only her echo remained forever within the CAL databases. He would always believe that she had died that first time they met.
Just because you believe something doesn't make it true.
He also believed that it was River's diary….