There was a mans speech in a TV talk show telling the audience that when someone get off the train could get back on and Detetive Drill thought about it, even he sought a notepad and write down that phrase, so to remember all the day, and at night time , when he would wake up and so on.
After a week of working out your mind with this method, found out a mirryade of ideas related to that note. Than Detective Drill realized the right reason why that long and clearly unresolved case could not be resolved. There was no new dreams in her life, nor other mind set of idea than the past, the rest is well known thougth Drill, the brain worked itself, changed the world by adding variables unknown and impossible to know.
Detective Drill called her friend and talked to her, after a few minutes she understood the case. There was not a case, it was an idea.