Discharged from the army as unfit, Antoine Doinel looks for his place in the world dealing with different work and tries to re-establish a relationship with his former girlfriend, Christine, without any success. After a short experience as concierge, he finds a job as private detective and takes a fancy to a woman he has under surveillance. In between shadowing and investigating, he will manage to give a sense to his research of inner stability, finding again the love for an old flame and a wiser self awareness.