After the prologue, the story kicks off after the last time we see Ten and Rose in the alternate universe together at The End of Time Part 2. It follows the Doctor and Rose's lives in this parallel world from Rose's perspective.
The wall between dimensions is closing faster than anyone thought it would. This is the story of what happens when they never make it back to Pete's World. AU Journey's End. Eventual OT3 RoseXDoctor Ten x Rose X Tentoo