A young woman is killed in a hit-and-run trying to ask for Harry's help, and he feels obligated to find out why. She was a student at the University of Chicago, so he tracks down her friends there. They live at Psi Phi Xi fraternity! (Sy Fy, get it?). Harry uses a very innovative (and disgusting) method of snooping on the frat: he implants magical bees in his ears and eyes (yuck!) and sends others in to be the "fly on the wall" to feed him information. Very squirm-worthy!
This turns out to be another case of "dark magic," which pings the radar of both the High Council and Bob's sense of decency. But Harry insists on following up in honor of the brave co-ed who died on his doorstep looking for him.
There is another touching scene where Bob is wallowing in self-pity and bemoaning his uselessness. Harry brushes aside his consternations in a frankly callous manner, but Bob finds it "strangely comforting." I think that was the phrase he used. Certainly something like that. They definitely have a fascinating relationship.
Turns out these frat bros are using a "La Main de Gloire" (aka, The Hand of Glory), a relic from a hanged thief, which lets them breach walls and steal stuff. But, like all magic, it is not without its costs. Especially if a breach closes when you are not all the way through it yet! Harry has to battle both the spirit of the hand, and the frat bros who are under its spell. Does he prevail? Well, this is a "no spoilers" review, so you will just have to see for yourself.