Demi-Tarif follows the low-key adventures of three young siblings, Romeo, Launa, and the youngest - Leo, left on their own in a rundown Paris apartment. One of them narrates, wistfully explaining how their mother abandoned them and calls them once in a while to see how they are doing or tell them she loves them. The three kids do as they please, roaming the streets, running out of restaurants without paying for food, and shoplifting from the local grocery store. They eat whatever and whenever they want, gorging themselves on sweets. They beg for change on the Metro and show up late for school in tattered, dirty clothes. All the while, they try to keep the fact that they are alone a secret from the world of adults.

Twenty-year old Adolphe finds himself drawn irresistibly to Ellénore, a married woman who is ten years his senior. Although she initially repels her young suitor’s unwanted advances, Ellénore soon yields to his charms and the two embark on a passionate love affair.