An audience member proposed marriage to Keira Knightley during the Oscar-nominee’s first preview performance of “Thérèse Raquin” Thursday night -- and ended up being removed from the theater in handcuffs.

The disturbance began minutes into the performance on Thursday night, when the young man — who many assumed was part of the show — proposed marriage from the railing of the mezzanine, according to reports.

Knightley, who is making her Broadway debut in the Roundabout Theatre Company's adaptation of Émile Zola’s 1867 novel, remained in character as an usher escorted the man back to his seat.

Security eventually escorted the man out of the theater, but not before he hurled a bouquet of flowers onto the stage.

Gabriel Ebert, who stars alongside Knightley, broke character in the scene, kicking the bouquet off the stage and into the wings. The audience responded with applause.

A short break in performance was announced soon thereafter.

“Roundabout takes the safety of their actors and audiences very seriously,” a spokesperson for the show told NBC 4 New York. “Extra security will be added beginning tonight. For obvious reasons, we cannot comment on the exact nature of the additional security measures.”

"Therese Raquin," written in 1867, is about a woman trapped in a loveless marriage who embarks on an illicit affair with a friend of her husband's. The story has been adapted into a 1953 film starring Simone Signoret and another last year starring Elizabeth Olsen.

The show officially opens on Oct. 29 at Studio 54.