Dora was stunned by this information. She stopped. 'Do you mean' she said, 'that they're completely imprisoned in there?' Mrs. Marks laughed. 'Not imprisoned, my dear,' she said. 'They are there of their own free will. This is not a prison. It is on the contrary a place which it is very hard to get into, and only the strongest achieve it. Like Mary in the parable, they have chosen the better part.