Every case the agency takes on is written up afterward as an official Case File, kept in order, one letter of the alphabet at a time. The files are stored in a leather case-file book on the treehouse shelf, which is heavier than it used to be.
Visitors may read the files. Visitors may not take the files, spill on the files, or draw mustaches on the suspects. That last rule was written for one particular visitor, who knows who he is.