In 2398, 19 years after the events of Star Trek: Nemesis, the USS Sunset Shimmer gets called to Deep Space 9 to help fend off a new hostile warp-capable species: the Aridaginatans, descendants of three 21st century sirens. The Aridaginatans then time travel 384 years into the past. The crew are aware of this: the space sirens want to kill the person the ship is named after, so they can erase the indestructible starship from existence. With the help of the 21st century Equestria Girls (including Sunset herself), another Federation starship, and a familiar omnipotent being, the Sunset Shimmer crew must stop the Aridaginatans before it's too late.