Being a tramp is not always a disadvantage. For example when there is a masquerade ball. Indeed wearing flea-ridden rags might just mean having donned a costume. This is what happens to two resourceful Brussels bums, La Cloche and Picolard, who manage to gain entry in a fancy-dress ball. Once there, La Cloche is mistaken by an oriental prince for a respected doctor. His mission will be to give care to a music-hall diva. Even more exciting, he is asked to vaccinate a whole troupe of showgirls. Trouble guaranteed.