The adventures of the Grace children pick up where they left off after Mallory and Jared rescue their brother Simon from goblins who have kidnapped him. Twins Jared and Simon Grace, along with their older sister Mallory, have just discovered that the goblins that kidnapped Simon were in pursuit of the Field Guide. The Field Guide is a book written by their great great Uncle Arthur Spiderwick, a man who formerly lived in the house they are living in and who disappeared in a mysterious manner. The Field Guide is an instructional guide filled with illustrations and observations about faeries, brownies, goblins and other magical cretures. The brownie named Thimbletack that lives in their house is very angry with the threesome, particularly Jared, due to the fact that they will not give him the Field Guide. Although Simon and Mallory think that the Field Guide is nothing but trouble, Jared is very attached to it and refuses to relinquish it.
As a result, Thimbletack is playing mean tricks on Jared such as tying his shoelaces together and tearing apart his bed. Jared comes up with the idea of visiting their great Aunt Lucinda in the asylum and asking her about the Field Guide. They figure since she used to live at Spiderwick and she is Arthur Spiderwick's daughter, she might have information regarding the Field Guide, her father's disappearance and the mysterious creatures that the children have observed throughout the estate. When the children visit Aunt Lucinda they discover that she was placed in the asylum due to her belief in faeries, goblins and other magical creatures. They realize she is quite sane. Like the children, Aunt Lucinda has seen Thimbletack and other magical creatures.
Aunt Lucinda, unaware that the children have located the Field Guide, tells the children that her father abandoned her family without an explanation. She warns the children that they are in grave danger living in the house and that they must leave Spiderwick. Jared is crushed when he discovers that a vengeful Thimbletack has stolen the Field Guide. After the visit to Aunt Lucinda Jared wonders if Arthur Spiderwick's disappearance was related to the Field Guide. Although Arthur Spiderwick disappeared over seventy years earlier, the children decide that they will pursue all avenues leading to his disappearance. Through a series of clues on map, the children retrace Arthur Spiderwick's tracks and are led into a realm that humans rarely get a chance to enter. The children come face to face with a shape shifting phooka who calls himself Black Dog of the Night and taunts them with riddles.
When the children come face to face with three lifesized elves they come to the realization that the Field Guide is desired by many magical creatures (for reasons they cannot fathom) and was the reason for Arthur's disappearance. The elves are very hostile and hint that Arthur may be living in their elf realm.
This report prepared by Sandra Calhoune