Sex. Greed. Sibling rivalry. Adultery. Treason. False accusations of incest. These words may bring to mind a daytime soap opera—"The Young and the Restless" mixed with "All My Children," perhaps—but they also describe "The Other Boleyn Girl," a sumptuous, if underdeveloped, period piece detailing the topsy-turvy lives of 16th-century sisters Anne (Natalie Portman) and Mary Boleyn (Scarlett Johansson), and the man in between them, King Henry VIII (Eric Bana). If the film tends toward resembling a summarized version of the story, and the plot points welcome high melodrama over a more understated tone, at least give credit where credit is due. Director Justin Chadwick and screenwriter Peter Morgan (2006's "The Queen") entertainingly milk the subject matter for all the intrigue it's worth, and lead actors Natalie Portman (2007's "Mr. Magorium's Wonder Emporium") and Scarlett Johansson (2007's "The Nanny Diaries") are forces of nature as decidedly dysfunctional siblings who don't know whether to love or despise one another.

When his aging wife, Queen Catherine (Ana Torrent), is found unable to birth children and, thus, cannot give him an heir to the throne, King Henry VIII elects the Boleyn family to the high court with the understanding that the recently married Mary become his mistress. Pressured by her family to accept the offer, Mary enters into an affair with Henry and soon has become pregnant. These turn of events do not at all please Mary's ambitious older sister, lady-in-waiting Anne, who schemes to steal Henry's affections, convince him to turn his back on Mary and their "bastard" child, blasphemously annul his marriage to Catherine, and wed her instead. Having the son Henry desperately needs, however, is not as simple as Anne expects.

Based on the historical novel by Philippa Gregory, "The Other Boleyn Girl" was probably made with the intentions of being Oscar bait, only for the powers that be to decide it didn't have what it takes to be released in December. Thus, the film has been given a late-February berth and comparatively little promotion. It is true that this is not Best Picture material, but that doesn't mean it's unworthy of one's time. Director Justin Chadwick sets the wheels in motion for what one suspects will be a drop-down catfight between Anne and Mary Boleyn, but then astutely turns the corner on this notion and gives unexpected depth to these sisters' complex relationship. Yes, Anne ultimately betrays Mary in a bid for the wealth and power she seeks, but neither of their hearts are made of stone. Mary strives to forgive and forget when Anne turns to her for help, while Anne, too late, learns to regret the irrevocable decisions she has made and finally pays for much more than she deserves.

As the deceiving Anne, Natalie Portman has the showiest role; she is the one who takes matters into her own hand at the expense of those she cares about. As such, Portman is exceptional, particularly in the taut and emotional latter scenes where the full breadth of what she has done (and not done) comes into focus. Scarlett Johansson has a more difficult part in that, as the less exposed and outspoken younger sister, her personal arc is primarily told through the silences of her character. She, like Portman, is close to faultless in her low-key but rapturous performance.

Eric Bana (2007's "Lucky You") isn't at all likable as King Henry VIII, an intentional and accurate reading of a man of power who, when it all comes down to it, is an undignified liar and philanderer. As Anne's and Mary's devoted brother George, Jim Sturgess (2007's "Across the Universe") commands attention without needing to do or say much. Suggestions that his character is homosexual—he reluctantly weds Jane Parker (Juno Temple) but refuses to sleep with her—are just that; this is an area of the story that was more explored in Philippa Gregory's novel. Finally, as the matriarch of the Boleyn family, Lady Elizabeth, Kristin Scott Thomas (2001's "Life as a House") is underutilized, rarely ever shown interacting with her onscreen offspring.

Unlike 2006's revisionist "Marie Antoinette," which stopped short of detailing the queen's demise, "The Other Boleyn Girl" does not shy away from Anne Boleyn's fate, sentenced to execution for accusations of treason and incest with brother George. As the film hurdles toward its conclusion, it ratchets up a surprising amount of tension and poignancy as the lives of everyone involved, as well as the future of England itself, are changed forever. Handsomely, sometimes claustrophobically photographed by Kieran McGuigan, "The Other Boleyn Girl" isn't the tell-all exploration of Anne and Mary Boleyn that it might have been—artistic liberties have definitely been taken, while too many events to count are glossed over—but it is fascinating in its depiction of a troubled relationship between sisters that is anything but black and white. This emotionally ripe angle to a tragic story that could have been told any number of ways is where the film gets its potency.