Matis, in his early twenties, is mentally handicapped from birth. His mother Maria lives with him in modest circumstances and devotedly cares for him.
The lives of the two follow a strict routine. Until disaster strikes: One morning, Lea, the neighbours’ daughter, lies murdered and undressed on the sun-bed in the garden. Matis gets entangled in contradictions and comes under suspicion.
The boy is arrested, and to the horror of his mother he confesses to the crime. But Maria firmly believes in the innocence of her son. She starts her own search for the true perpetrator, laying her job and their existence on the line.
Soon, Lea’s swimming coach Sebastian Kreutzer comes under suspicion. Many years before, he had been convicted for sexual coercion of a student. When the latter commits suicide while in custody, the case appears to be solved. Matis is released.
But then the drama takes an unexpected twist, as Maria is blackmailed by her son’s bus driver with new evidence. Maria has her back to the wall: How far will she go to defend the innocence of her son?