Two years have passed since the Baltimare Incident. Another island has been used for more dinosaurs displacing to Equestria since the golden Crystal Mirror hasn't been fixed up yet. However when Scootaloo's parents offer Princess Cadance and Shining Armor a chance for them to go for a holiday for much needed rest during the ruling of the Crystal Empire, they couldn't say no. However once on the island things begin to go horribly wrong. Their hosts aren't who they claim to be, and now Cadance and Shining must survive the horror Twilight had faced before on the new island.

A year has passed since the golden Crystal Mirror was damaged, teleporting dinosaurs into Equestria every time it flickered to life. Following the chaos, Princess Celestia, Princess Luna, Princess Cadance and Princess Twilight Sparkle ordered all displaced dinosaurs to be relocated to Isla Unicorn-an isolated island southwest of Equestria-where they could live freely, away from the civilization. Now Twilight must lead her friends to the island in order to preserve the dinosaurs on it and prevent their exploitation by the Storm Kingdom who somehow had found out and had plans to weaponise them.

During a game of hide-and-seek with Flurry Heart, Princess Cadance stumbles upon a mysterious Crystal Mirror hidden deep within the Crystal Empire. When she and Shining Armor alert Princess Celestia, she entrusts Twilight Sparkle with the task of investigating the strange artifact. But the investigation goes horribly wrong. A single misstep hurls Twilight through the mirror and strands her on a remote island teeming with creatures that should have been lost to time. Now, with no way home and predators lurking at every turn, Twilight must summon all her courage and wit to survive. As she struggles to uncover the island's secrets, she discovers that some mysteries are far more dangerous than they appear.