As Luna and Celestia prepare for the Summer Sun Celebration, they disagree on whether or not to tell Twilight how powerful they really are. In the human world, a physicist named Gordon Maxwell experiments with a device that could potentially provide unlimited clean energy to Earth. However, Gordon's good intentions result in a disaster that threatens to destroy Equestria's magic at its most fundamental levels, one which also also awakens a dangerous and unpredictable enemy. Twilight, her friends, and a pair of unlikely allies must work together to repair the damage before Equestria itself is destroyed.