The girls have returned from camp with new friendships, new powers, and new concerns and hopes. Twilight and Sunset ask them all to come to Sweet Apple Acres house to take part in an experiment, minus the magic balloon torrent and rainbow explosions with any luck, and try to learn just what they can all do now and what they should be doing with their powers. But plans don't always go as expected, particularly when the fabric of reality gets torn asunder above you.

In a similar but at the same time very different world Progenitor Liam Harcourt and his people find themselves the victims of a surprise attack. Hammered by weapons they have no defense against and with complete annihilation a very real possibility they have no choice but to evacuate and rebuild their strength. First though they'll have to make it past the gauntlet of mankind's wrath and they're throwing everything they can at them.

Unbeknownst to both, in darkness malice and strife embodied is stirring from centuries of sleep. It's made its plans, placed it pieces on the table, and now waits for the chance to break free from the bounds that shackle it. All it needs is the right key to free it, and it may have found just the one.

Whether the meeting of this group of magical friends and the outcasts of a wounded Earth is in peace or rage may very well decide the fate of both their worlds.