The Grace twins are dragged from New York to the inherited, run-down Spiderwick estate with clueless but bossy elder brat sister Mallory (Sarah Bolger) as their divorced mother Helen (Mary-Louise Parker) couldn't afford her old job at city prices. Shy nerd Simon (Freddie Highmore) resigns to thinks, but adventurous brother Jared (Freddie Highmore) stubbornly revolts, then finds presumably deceased uncle Arthur Spiderwick's (David Strathairn's) life's work "field guide to the magical world", is stunned when the creatures it generally warns against actually inhabit the estate and explores further. Honey-addicted tiny book guardian Thimbletack (Martin Short), who lives indoors, explains it most at all cost be kept away from ogre Mulgarath (Nick Nolte) and his army of trolls et cetera, which a magical circle keeps outside, but his clueless siblings draw them there. Rescuing Simon, Jared meets and teams up with bird-eating Hogsqueal (Seth Rogen). The ensuing battle under siege is the start of further adventures, involving Arthur's mental asylum-bound daughter Lucinda Spiderwick (Dame Joan Plowright), who divulges more surprises, while the ogre's forces stop at nothing to conquer he book for control of the magical world, which Jared gets to penetrate further then he could imagine.