Ponyville has stopped communicating with the other cities, and rumours that a battle has broken out within the town. To add, Celestia hasn't received word from Twilight in months. Unfortunately, she, her sister and the Captain of the Royal Guard, Shining Armor, are too weighed down by duties to head to Ponyville.

The only pony left for the job, Princess Cadence, is ordered by Celestia to find out why Twilight has stopped writing to Celestia, but plans change when she finds out what's really going on, as well as unexpected companions.