The owners of Alton Towers theme park could be punished over an accident which seriously injured five people last year.
In 2015, the Smiler rollercoaster crashed with 16 people on board.
The 500-acre theme park was shut down for four days after the accident, and Alton Towers say that it has improved its safety measures since then.
But now the owners, Merlin Attractions, will have to answer questions about whether they broke rules that are there to keep people safe when the crash happened.
Accidents on rollercoasters are very rare.