Director Guillem Morales tries to mislead the audience with too many plot twists, but in doing so he diminishes the effectiveness of his thriller.

Early in "The Wasp," Naomie Harris offers an extended description of tarantula hawks, a species of spider that feeds on other tarantulas, paralyzing their prey before eating them alive. It's a horrifying idea that writer-director Guillem Morales clearly wants to revisit in his intricate two-hander, which stars Natalie Dormer and Harris as two former friends locked in a cat-and-mouse game of violence and intimidation. Unfortunately, Harris's monologue is the film's high point. None of the plot twists — and there are far too many — manage to reach that crescendo of mounting dread.

Harris is Heather, a wealthy, childless Londoner in a strained marriage to Simon (Dominic Allburn). In high school, she was friends with Carla (Dormer), now a supermarket cashier with four children, a fifth on the way, and a hopeless drunken gambler for a husband. The disparity in their social and economic positions serves as an obvious plot motivation for Carla to be desperate to take what Heather is offering, though Morgan Lloyd Maclolm’s screenplay, based on his play of the same name, fails to use it to complicate the characters or their relationships with each other.

Malcolm is more interested in using motherhood and pregnancy as metaphors in dialogues that are filled with references to wasp behavior. While Heather desperately wants a child of her own, Carla would easily give one up for financial gain. The origins of their turbulent relationship are revealed in flashbacks. As the film unfolds, Heather offers Carl a way out of poverty, which of course comes at a high price. The audience then sees how their friendship became antagonistic and why neither can trust the other to be honest.