Lou Bertignac has an IQ of 160 & a good friend in class rebel Lucas At home her father puts a brave face on things but cries in secret in the bathroom while her mother rarely speaks & hardly ever leaves the house To escape this desolate world Lou goes often to Gare d' Austerlitz to see the big emotions in the smiles & tears of arrival & departure But there she also sees the homeless meets a girl called No only a few years older than herself & decides to make homelessness the topic of her class presentation Bit by bit Lou & No become friends until the project over No disappears Heartbroken Lou asks her parents the unaskable question & her parents say Yes No can come to live with them So Lou goes down into the underworld of Paris's street people to bring her friend up to the light of a home & family life she thinks