Are there specific answer choices? This could be interpreted different ways. The way I see it is, insanity gives the feeling of being locked in a cage. But, it depends and varies on what kind of "cage", meaning what is it that traps this person, making them insane. What has driven them to that point, what makes them feel trapped. That is their cage. Many have different cages. Maybe stress, depression, or something specific going on in their lives. As far as "who has who locked" means that each situation differs by what place that person holds. Maybe they may be the one insane and locked in their cage, or they may be the one locking someone in a cage. Two different situations created by switching roles. Sorry, I'm probably not much help but this could mean many different things depending on your grade level and what exactly is needing to be understood, as well as how deep. I hope you find your answer ^^