'Belle' (PG)

Inspired by the true story of the mixed-race daughter of a Royal Navy admiral in 18th century England, Belle is a costume drama with historical and cultural relevance. The film touches on the subjects of class, responsibility, race and the slave trade, and the importance of standing up for your principles. And yet it still feels a little like a lesson you’re supposed to learn before you can enjoy anything truly satisfying.

The film centers on Belle (Gugu Mbatha-Raw), who comes to live with her great uncle Lord Mansfield (Tom Wilkinson) and his wife (Emily Watson) after her mother dies and her father’s ship goes back to sea. Belle is raised with her cousin Elizabeth (Sarah Gadon), and the girls are inseparable but not equal: When guests visit, Belle must eat alone, too controversial to mix with society but with a status too elevated to dine with the servants.

As the girls approach marriageable age, Belle feels this separation keenly — there is talk of suitors for Elizabeth but never for her, although only she has an inheritance — but soon she’s distracted by the appearance of young law hopeful John Davinier (Sam Reid). A passionate abolitionist, he educates Belle about a case on which her uncle will rule: the infamous lawsuit involving the Zong slave ship. The crew killed 142 slaves, claiming the water supply was running low, and the slavers want insurers to pay for the lost cargo. Belle finds herself drawn to Mr. Davinier — and not merely because of her personal interest in the Zong.

Belle presents an interesting history lesson, one that had significant repercussions, but some of the developments in this storyline turn out to be woefully convenient. The film also gives short shrift to an intriguing economic conundrum that develops: One suitor, realizing that Belle has a fortune of her own, finds his distaste at marrying the daughter of a slave fading quite nicely the more he thinks about her money, a paradox that deserves more investigation.

The display of racist evil comes in the form of Miranda Richardson as the dreadful but opportunistic mother of Belle’s suitor and Tom Felton in full Draco Malfoy mode as his equally bigoted brother. Villains are required, of course, but Felton is so over the top that he’s not even fun to hate. The rest of the cast is solid, but for all its good acting and interesting story, Belle never fully engages you emotionally. It’s a good and important story, forgettably told.

Cast: Gugu Mbatha-Raw, Tom Wilkinson, Emily Watson, Miranda Richardson, Sam Reid, Penelope Wilton.

Director: Amma Asante.

Screenwriter: Misan Sagay.

A Fox Searchlight release. Running time: 104 minutes. Thematic elements, some language and brief smoking images. Opens Friday May 16 at area theaters.