When Yvon Rioux, a teacher and singer, witnesses the brutal death of a former student, shot dead before his eyes, his world falls apart. Traumatised, he develops post-traumatic stress disorder, which turns his life upside down and reopens old wounds. Haunted by the silence of his grandfather, a Second World War veteran, he decides to travel across Europe to confront his fears, understand his past and begin to rebuild his life. Une dernière cicatrice is an intimate portrait of a man in search of inner peace, between memory, transmission and resilience.