I’m looking for a specific fic that was on ao3. It’s jack/ianto, and has eleven, Amy, and Rory. It takes place during the episode when jack returns from the year that never was. Eleven takes the tardis back to that evening, and meets the TW team on top of the building where John hart came through the rift.
Eleven tells jack that he has to sacrifice Gwen to the rift or ianto will die. Jack pushes Gwen (and John because they were handcuffed together)into the rift, and the bomb that was on John’s chest exploded, closing the rift. Time resets, and everyone goes to a hotel, where eleven explains that Gwen was never supposed to exist.