Mildred Hayes, who lives in a small town, kills daughter, Angela. Now she only dreams that the criminals were found and severely punished. But the police seem to be in no hurry to fulfill their direct duties. Several months have already passed since the murder, but there are no suspects. A desperate woman in response to the inaction of the sheriff and his assistants decides to take an unusual step - she rents three billboards located at the entrance to the city, and expresses her indignation on them. By her actions, the woman wants to draw attention to the case and stir up local law enforcement agencies, in particular, the chief of police, William Willoughb, who enjoys great prestige among residents. However, instead, it causes anger among the law enforcement officers.
Legal methods to remove billboards is impossible, so the police in every way spoil the life of Mildred. Literally the whole city is opposing the woman. But an angry mother quickly shows that she is quite capable of standing up for herself and repelling anyone who crosses her path. Gradually, the situation in the city is heating up and the real war begins. And, as in any war, there will be no casualties here. Three simple billboards start a series of crazy events.