We are not sure if we could say that the spies do good or bad job. Living among people with a false identity and collecting information about those people or the acts of certain organizations, cities or states does not sound as something positive.
On the other hand, those people are usually very intelligent people, they know many foreign languages, they are very skilled in few fields and they do good for the organization that hires them. still, many of them have task to collect information and help destroy certain entity, no matter in which field of interest.
Donald is a detective that is on a very delicate and secret mission. Namely, he has to reveal the identity of the man who works as a spy for another state. After a long investigation, Donald gets to the place that could be the secret hideout of the spy. That means that this place hides numerous traces and evidences that are probably well hidden but Donald will do his best to find them and use them for revealing the real identity of the spy.