Young Frenchwoman Jane (Caron) is living in London and has an affair that leaves her pregnant. She winds up moving to a tacky boarding house, into the small room of the title. Soon, Jane has fallen for fellow tenant, out-of-work writer Toby (Bell), without disclosing her situation. However, when Toby's jealous best friend, jazz musician Johnny (Peters), learns of Jane's pregnancy, he uses his knowledge to break the twosome up. In the kitchen-sink tradition of British films that doesn't expect a happy ending. Based on the novel by Lynne Reid Banks.