Our heroes return for another mystery/adventure in "The Case of the Simple Soul," in which the kids investigate a series of barn arsons and the appearance of a mysterious troll-like person under a bridge. Meanwhile Shauna and Jack are dating and it's thrown the group dynamics into turmoil. One thing I really appreciate about [a:John Allison|390509|John Allison|https://images.gr-assets.com/authors/1442466472p2/390509.jpg]'s Bad Machinery is that the characters aren't stuck in time - you can actually see them slowly growing up from volume to volume, with the girls maturing a bit faster than the boys. My main issue with this volume is that some of the transitions between scenes felt a bit confusing.