This story is based on the orginal idea of the Snow Queen story, originally planned with the first concept of Frozen.
Prologue...
My name is the Doctor. I am from a race known as the Time Lords. We have the ability to travel through time and space, and can live forever. Well, mainly...
I speak to you currently in my eighth incarnation. I was put under the wing of the Royal Family of Arendelle, under the order of King Agdar and Queen Idun. My duty? Guardian of the King and Queen's daughters, Princess Elsa and Princess Anna. That was back in my sixth incarnation.
During my travels I later returned, discovering that Elsa had the powers to control Ice and snow. I made a terrible mistake, not training her to control her powers. Alas, I returned many years later to hear the King and Queen had been tragically killed in a shipwreck. I made a selfish choice, and left the time line to run its course.
I returned in my current incarnation to find out the girls had spent nearly ten years separated due to Elsa's incapability to control her powers. Well, to make up for my selfish choice of absence, I taught Elsa to control her powers with her own will, using our Time Lord magic. Myself, Anna and Elsa became like family.
That was not to last. An old enemy and former Time Lady, the Rani attacked Arendelle. Alongside her was the Dalek's. My arch enemies! All of my past and future selves fought alongside one another to defeat her, and the Dalek's. Saving Adrendelle, and the world!
But we made a terrible mistake. During the rush to defeat the Daleks, the Rani escaped in her own Tardis. Shortly after I left the girls she remained hidden and created a rip in the fabric of space and time, opening a worm hole to an alternative time line. In this time line, Elsa is pure evil and Anna is out for blood thirsty revenge. The evil version of Elsa captured the good version of Elsa, and held her captive.
I received a frantic call from Anna, saying her sister had been kidnapped and she needed my immediate assistance.
This is what happened...