First, there's Harry Potter, famous in the wizard world for defeating and stripping Lord Voldemort of his powers.
Then there's One Direction, famous in the human world for their songs, especially their number one hit What Makes You Beautiful.
Everyone knows what happened from the first to the seventh books.
Now, let's rewind back to Harry Potter's first year and throw One Direction in it. While everyone is sorted into the houses, 1D gets split up and Harry Potter and Harry Styles are put into the same house. Now they have to team up with all the other houses to bring down Voldemort once again.