Where does Joe imprison the people, he needs to get out of the way in the novel, You?

A cage is located in the basement of the bookstore where Joe works. Its purpose is to keep the rare books on sale at the store safe from theft. Because the cage is so large and is fitted with a bathroom, Joe uses it as a prison for the people he feels he needs to get out of his way. Candace’s brother, Benji, and Beck are all kept in this cage at one point. None of them leave the bookstore alive.