The Secret of NIMH is a thoughtfully animated and relatively mature—if sluggish and oft unfocused—adventure about doing everything you can for your loved ones in the most dire of circumstances. Field mouse Mrs. Brisby (voiced by Elizabeth Hartman in her final role), widow to a much mentioned Jonathan Brisby, lives in a cinder block with her several children on a farm-owned field. With farming season arriving soon, Mrs. Brisby intends to move her family elsewhere, but her son Timothy falls sick with pneumonia and cannot move, according to family friend and her dead husband’s friend Mr. Ages (Arthur Malet). Mrs. Brisby then befriends Jeremy (Dom DeLuise) a clumsy but loyal and confident crow, who helps her make a new plan after she and a neighbor soon after have to disable a tractor from destroying her home earlier than anyone expected. Together they visit the Great Owl (John Carradine), a mystically wise being who never sees anyone else without killing them. With Mrs. Brisby, however, upon hearing her late husband’s name, reveals he knew Jonathan and thus tells Mrs. Brisby to visit Nicodemus (Derek Jacobi), the magical and intelligent leader of an abnormally smart clan of rats. Together with Jeremy, Mrs. Brisby discovers a larger conception of rebellion, willpower and escape through loyal rats willing to do anything for each other—and eventually her kids.

NIMH’s greatest strength is also its greatest weakness. In Don Bluth’s directorial debut and Hartman’s heartfelt final performance, NIMH is packed to the teeth with subtext about escaping your past, harnessing your greatest strength and coming together with everyone around you no matter what. From deftly muted color schemes of the worn-down underground structures made from human leftovers and scrap metal, viewers get thrown into a world of relentlessly dangerous poverty. From the get-go, Mrs. Brisby sees the solution as being those around her: “Run! The plow is here! Run for your lives!” a usually paranoid and crude Auntie Shrew (Hermione Baddeley) says before braving a daring tractor sabotage for Brisby and her family. This hopeful and engaging theme runs throughout, especially as Mrs. Brisby meets the rats, their togetherness shines consistently and particularly in the second half, as shadier characters like the power hungry Jenner (Paul Shenar) gets introduced to try and fail at dividing them for his own gains. “I’ve learned this much, take what you can when you can,” an angered Jenner belts, defying everything NIMH has thus far demonstrated. On top of solidly embellishing performances all around and top-notch classic animation that draws viewers into even the dullest parts, NIMH’s secrets are as twisty as they are entertaining.

Unfortunately, these same secrets are also what make NIMH a bit of a lull. There are simply too many well-defined characters and subplots to make much sense of; at one moment, characters face a sinking cinder block they must rope out, before there’s a bit of a lackluster and mostly music-less transition to the next big event. The NIMH acronym, standing for the National Institute of Mental Health, for example is also an entire subplot not explained prior because it’s the most underdeveloped component of the film. With no central character either—Mrs. Brisby is the main, but certainly not the focus—each vital sequence takes more effort to attach to others in terms of importance and connectivity. In short, it can feel a bit disjointed and more like a showcase of dazzlingly hand drawn animation and pure ideas than a solidly crafted narrative. Regardless, The Secrets of NIMH is rich in concept and aesthetics, making it a fine pick for animation fans, fantasy fans, Don Bluth or Elizabeth Hartman fans and those looking for something surprisingly bittersweet.

Screens on Mother’s Day, 5/11, 12:30 p.m. @ The Brattle Theatre