Every file is fictional, complete and checked so that one answer survives every record. Difficulty reflects how many documents you must connect, not how much you must guess.
One case $9.99, or every case with a plan. Guests in your room never pay.
Each file begins with the answer: who, with what, why, and the minute-by-minute sequence. Then the documents are written backwards from it, so that every record is internally consistent and the killer is caught by at least two of them. Every other suspect is given a real motive and a real alibi that a specific document confirms. Finally the folder is read cold by someone who does not know the answer, and anything that gives it away for free is removed. What remains is the file.