Johnny is on a trip with Professor Childermass (which becomes an ongoing theme in the novels; the two are almost always going off on some jaunt or another), touring the mansion of late cereal magnate H. Bagwell Glomus, when they're shown the man's office and the clues he left to his hidden will left behind in his office....a chess set, a tavern sign, and a Greek newspaper. Johnny puzzles over this as a hobby, especially after learning there's a substantial reward going out to anyone who finds it. And he's given further reason to find it....his grandmother is taken ill, and it turns out she's got a brain tumor that requires surgery.
To get his mind off things, Johnny sent to a Boy Scout camp near Mount Chocorua (a real place, and it looks impressive), only to find that that Glomus' summer house is nearby....and it matches some of the clues left in his office. With his new friend Fergie, aka Byron Q. Ferguson, he slips out at night to investigate, where they meet one of Glomus' nephews, a rather strange and slightly disturbed young man. After threatening them, he then shows them a secret passage, and tells them a spooky story of a strange magical guardian who haunts the house. And then there's a hideous scream...
This is a fun tale, where Johnny gets in over his head when panic and anxiety take over and he's not able to think clearly. He ends up going off on a half-cocked quest to find the will, running afoul of Glomus' scheming family and the eerie guardian that tries to keep him away. There are a few contrived bits but the magic rituals involved in raising and controlling the guardian are interesting reading, with some fun little details that stick in the imagination. And yes, the title is given full relevance in the course of the story.
A good, solid entry in the Bellairs canon, if not as shuddersome and eerie as some of the others, but worth searching out.
