In Bern, Sylvia Leiser has been working for 35 years in her car as a prostitute. She is known as "Mrs. Mercedes," after her place of work. She has been directly confronted with the transformation which took place in the underworld: Brothels have been rendered legal, with the paradoxical consequence that the business doesn’t submit to any more laws. Prostitution is now socially acknowledged, but at the same time has lost its glamour, and the profits are no longer what they used to be. The number of customers is always the same, yet in Bern, the number of women working in the underworld has increased tenfold. Today, Mrs. Mercedes earns in one month what she used to earn in one day. The documentary "Lady Mercedes" is a portrait of the prostitute Sylvia Leiser. The film accompanies her to the part of the town where she works in Bern. There, she offers her services every evening of every week. The film shows her also in her flat in Biel, where she is known as Mrs. Leiser, and lives modestly and rather lonely in an unassuming block of apartments. By interviewing her and meeting with people of the underworld and acquaintances related to her private life, we get the opportunity of approaching the privacy of a prostitute—of understanding the meaning of daily and normal life for someone who lives in rather peculiar circumstances at the borders of society.