strike at the root of something

Exploration Stage: Capuchin Movie Theater
From: Lewis Capuchin
Description: It is dangerous to turn off or attempt to repair the projector right now. It could put your audience in terrible danger for just a little while. When this happens, the only thing to do is to cut off the root of the problem. Let's examine the film that the culprit set in the projector.
Completed: It appears that the only film that has been burned is the film that was there before. This means that the only film that is creating the illusion of a monster is the film that the culprit put in. Wait for this to be finished and remove it. Look for the next film to be reproduced in the vault.