It's 1940 in Berlin and working class husband and wife Otto (Brendan Gleeson) and Anna Quangel (Emma Thompson) are doing their best to ride out the war. When they receive a telegram telling them that their only son has been killed fighting on the front, however, everything changes.

Otto decides to focus his rage and grief into writing postcards emblazoned with anti-Nazi slogans, calling Hitler a liar and murderer, and advising people to stop the war machine and overthrow Hitler. He decides to risk everything to disseminate these messages of protest across the city, leaving them on steps of buildings, in mailboxes and other public places, wherever people will see and read them. When Anna discovers what he's doing, she joins him in his act of subversion.

Although small and covert, their protest rattles the regime, including a police inspector (Daniel Brühl) who will not rest until the people responsible for the messages have been caught and punished.

Based on the true story of Otto and Elise Hampel.