Possession (1981)

Mark, a Kiwi spy residing in West Berlin with his French wife Anna and their son Bob, grapples with the disintegration of their marriage. Anna's desire for a divorce leaves him shattered, unable to comprehend the reasons behind her discontent. As their relationship unravels, Mark's desperation drives him to extreme measures to uncover Anna's hidden life. However, this pursuit unearths a dangerous secret, and Anna becomes more and more dangerous.