Anna Friel has joined Neil Burger's thriller The Dark Fields, starring opposite Bradley Cooper in the Relativity pic.

According to The Hollywood Reporter, the story centers on a down-and-out writer (Cooper) who gets his hands on a top-secret pharmaceutical drug that makes one smarter. He experiences sudden financial and social success but soon discovers that the drug has lethal and lasting side effects, including "trip-switching," a phenomenon in which time moves with a stop-motion quality. Before long, mysterious antagonists are pursuing him.

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Friel will play Cooper's ex-wife, a woman who was a go-getter before their breakup.

Robert De Niro and Abbie Cornish already are cast in the movie, which Universal will distribute via Relativity's Rogue Pictures.

No production date has been set.