Lydie, a physically unattractive young woman, is brutally dumped by her fiancé when she had just acquired the lease of an apartment to live with him.

A young Parisian advertising executive becomes so captivated by the unsettling charm of his mysterious new employer that he eventually abandons his family and friends, viewing it a privilege to let the ubiquitous employer take over his home, his life, his desire. Only his wife remains suspicious, recognizing both the pathos and the evil in the man’s soul-stealing power.

After the birthday party of his wife Odile, Louis accompanies a friend to the station. When the train leaves he starts reminiscing about his youth.