Chapter Two, Act Two: Murder on the Owl Express
Upon making your way to the front of the train, you will find a present box with the Detective Hat inside. Immediately wearing it will signal a phone call from the nearby phone, letting you know your dear father's sister (which is the name you gave the CAWs or AUNTIE by default) is waiting for you in the back of the train. When you get there, a murder has been committed and it is up to you to find the culprit!
That being said, this trophy kind of goes against it. Littered throughout the train, as you scurry from the back across previously inaccessible rooms, are CONFIDENTIAL folders that contain the clues you need to accuse someone. Each folder will give you a new suspect to incriminate, but you need to avoid all of them and go through the discovery of each room as if you were initially looking for them. The timer doesn't clock down constantly; only when you enter/exit specific rooms in search of the clues will it count down. That means that, in order to complete the act, you must still make it all the way to the locked KEEP OUT room that is in the heart of the train, guarded by the rest of the CAWs. By exiting this room without getting the folder, you will be taken back to the crime scene and will be able to accuse one person, giving you the trophy as well as finishing the act with a low score.