Revealing mistake: When Jared is first reading the field guide, in flashback, there is a shot of Mulgarath in crow form trying to take the book from Arthur Spiderwick. Later in the movie, when Jared is about to burn the book, the same shot of Mulgarath is used again.
The Spiderwick Chronicles (2008)
1 revealing mistake - chronological order
Directed by: Mark Waters
Starring: David Strathairn, Freddie Highmore, Mary-Louise Parker, Sarah Bolger
Continuity mistake: In the scene where Hogsquel gives Jared "the sight", after he spits in his eyes Jared is holding the seeing stone, but in the next shot when he is wiping the spit from his eyes the stone is gone.
More questions & answers from The Spiderwick Chronicles
Chosen answer: The book was full of the secrets of the hidden world. If Mulgrath had it, he could destory all the other creatures.