The mastermind's plots and their related crimes are finite and will eventually repeat. They are selected at random at the beginning of each game, but after handling enough cases, you will start to recognize the same old crimes and plots early on as they unfold.

What IS entirely random is all the details of each case. It will be random suspects with random faces and random jobs, from random addresses from random organizations in random cities, working with random allies, etc. etc. every time. So you'll still have to work to figure all that out to bust a case. But if you play through enough cases, you'll come to recognize all the crimes and pretty much know what the mastermind's plot is very early on. Which, again, won't win the game for you, since there are still a lot of variables.