Not only is Pinkie Pie accused of murdering ponies in Equestria, but also attempted murder of the sister of one of her best friends, and only Twilight has enough faith in Pinkie to defend her.
As Pinkie acted strange during Cadance and Shining Armor's visit, her friends begin to suspect what her secret is. They didn't realize how close, yet so far, they really were.
With their futures beginning to look bleak, The Dazzlings decides that it's about time that they return to Equestria, but not only has their old home changed, but they found that they themselves have changed more than they expected.