Gatsby a shot and Nick goes to therapy. Nick's therapist thanks it would be a good idea as part of his therapy to write down the story of Jay gatz so the story is like his therapy and it is told through his point of view like as if he was describing it to the therapist
To ask people to step in a situation if someone is picking on them
I think the excerpt you are talking about is...
"Dantès entered the second grotto. The second grotto was lower and more gloomy than the first; the air that could only enter by the newly formed opening had the mephitic smell Dantès was surprised not to find in the outer cavern. He waited in order to allow pure air to displace the foul atmosphere, and then went on." from The Court of Monte Cristo.
A synonym or the word grotto could be cave/cavern. Hope this helps!