In a London boarding house, a number of lives exist precariously on the edge of disaster or despair. Stasia, the housemaid, hungers for happiness but is treated like a drudge and constantly threatened with a return to the punishments of her youth. Vivian, a beautiful young girl, loves the architect Chris, but must marry the repugnant Mr. Wright in order to erase her parents' debts. Miss Kite derides all around her out of fear of aging and loss of beauty, while her friend Mr. Larkcom sells mediocre phonograph records though he'd secretly love to be a concert pianist. Into the lives of these and other unhappy residents comes a mysterious stranger, under whose influence they each begin to see the possibility of happiness. But the cynical Mr. Wright prefers to see them in misery and plots to thwart the angelic stranger who lives in the back room of the third floor.