During what should have been a normal day at U.A. High, a group of Class 1-A students and several pro heroes are suddenly caught in an unexplained dimensional phenomenon. Instead of landing somewhere else in Japan, they find themselves on a completely unfamiliar barrier island off the coast of North Carolina.

Kildare.

At first, everything seems relatively normal.

There are beaches, boats, houses, tourists, and teenagers.

Then they discover the island is divided.

On one side are the Pogues—the working-class kids from the Cut who live by their own rules and have a habit of getting into trouble. On the other are the Kooks—the wealthy residents of Figure Eight, complete with expensive boats, private parties, and a long-standing hatred for anyone from the south side of the island.

And somehow, the MHA characters arrive directly in the middle of all of it.

John B, JJ, Pope, and Kiara are already occupied with the mystery surrounding the Royal Merchant, John B's missing father, and a growing number of people who seem far too interested in what the Pogues are discovering. The sudden appearance of strangers with impossible abilities only makes their situation more confusing.

To the Pogues, Quirks look like something straight out of science fiction.

To Class 1-A, the fact that they have somehow been transported to another world without explanation is already bad enough—but being immediately dragged into a treasure hunt involving a missing father, a sunken ship, wealthy enemies, corrupt secrets, and a mysterious compass makes things considerably worse.

The crossover follows both groups as the MHA characters attempt to understand how they arrived in Kildare and find a way home while becoming increasingly involved in the Pogues' search for the Royal Merchant treasure.

Meanwhile, the Kooks become suspicious of the newcomers, especially after witnessing abilities that should not be possible.

Rafe sees powerful strangers as either a threat or something that could be useful.

Topper immediately dislikes several members of Class 1-A.

Sarah becomes curious about the outsiders and finds herself caught between the two groups just as her relationship with John B begins changing.

And Ward Cameron becomes increasingly interested in the appearance of people who possess abilities no one else on the island can explain.