The 30-year-old actor, who co-stars with Weisz in the Roger Michell-directed film as her cousin Philip, said he is awe of the actress as she played her character to the T, reported The Independent.
"What Rachel brought to Rachel was this incredible kind of mystery and dark, kind of Gothic, undertone. She left me on the edge of my seat, watching her and witnessing her performance. I totally was swept up in the magic of it," said Claflin.
The film, which is based on Daphne du Maurier's novel of the same name, released on June 9 and also stars Iain Glen and Holliday Grainger.