Our final detective story trope uses ingredients from all of the ones mentioned: The hard boiled narrator can’t take a job at face value. Their cynical, investigative nature won’t let things slide. They look at the client, the job, weigh up the clues, mix it with some experience and gut feeling, and decide that none of it adds up.
It's also a good time to summarise the evidence that's been provided up until now. Can you see this pattern in these examples?