In Secret Elizabeth Olsen, Oscar Isaac, Jessica Lange. Directed by Charlie Stratton. Rated R. Opens Friday.

Émile Zola’s 1867 novel Thérèse Raquin has been adapted numerous times to stage, screen and radio, and In Secret (originally titled Thérèse) is the latest version. Writer-director Charlie Stratton sticks close to the events of the novel, but his tone is decidedly skewed, taking a tragic story of guilt and repression and turning it into a campy potboiler.

Elizabeth Olsen stars as Thérèse, an orphan taken in by her domineering aunt (Jessica Lange). Forced into a loveless marriage to her sickly, sniveling cousin Camille (Tom Felton), Thérèse enters into a torrid affair with Camille’s friend Laurent (Oscar Isaac), and the two soon conspire to get rid of any obstacles to their love.

The movie’s first half struggles between period-drama classiness and something a little trashier, but the second half is full-on camp, with ghoulish effects sequences, tongue-in-cheek performances (Lange manages to chew scenery even after her character is incapacitated by a stroke) and cartoonishly heightened emotions. Olsen holds things together well as the increasingly unhinged Thérèse, but it’s hard to tell whether Stratton means for the over-the-top melodrama to be taken seriously. Either way, it ends up being perversely entertaining, although Zola probably would not have approved.