The best way I can start is to say that this 19th chapter is not a defining film like "Pirates Ahoy," but it is surprisingly well done and deep.
I call # 10 "Pirates Ahoy" the defining film because an innocent sea cruise turns into a dire situation when Fred's parents were kidnapped. Fred (the leader) finds himself on his own (except for the gang of course) and one other person, Velma's perception finds some important clues, at one point Daphne (in a girly fashion) helps them. (She cuts ropes with her credit card.) Shaggy and Scooby start off in their comical and cowardly fashion, but they rise to the occasion and help save the day. And Fred steers the gang through a dangerous situation, and saves everyone. Fred also gives Scooby the final command to take them home, and Scooby gets the last word.