Force of Habit follows the lives of various women throughout one day. Hilla is having a romantic vacation, Emmi is throwing a house party, and Milja is on her way to school when they’re approached by a stranger and things take an unexpected turn. At the same time, Emppu, a young actress, is conflicted as she rehearses for the biggest role of her life. Elsewhere, Aleksi, an inexperienced prosecutor, is preparing for his first court case in haste; Niina, the victim of the crime, has been waiting years to see her case tried. Miia throws a company party, and the mood dramatically changes when her colleague Katja opens up about their boss coming on to her. Miia and a couple of her closest colleagues try to resolve the situation, but how do the others react?

Group of old friends gather in a summer villa to celebrate a surprise birthday party for Mitzi, who is the dramatic focal point of the group. The weekend starts ominously when Mitzi does not respond well to the surprise party. It turns out that Mitzi has just filed for divorce and has been looking forward to a peaceful weekend. The tense situation takes a new turn when Mitzi’s best friend brings her new boyfriend for a visit, who happens to be a Swedish film star. Familiar surroundings and the old rituals get to the core of the group and make them forget their adulthood. Revelations, not meant to harm the balance, make them reassess their past as well as their present.