Elm Tree Terrace is host to an odd collection of guests. Colin Jepson, a young graduate from Sydney, turns up unannounced to look for a room. Mary Mercy who checks his references puzzles Colin: she is not English, but perhaps European, yet her dress belies this. Colin is entranced by her eyes. The other guests at the boarding house fit their stereotypes: a middle-aged school teacher from Scotland and a couple visiting from Adelaide. The boarding house manager, Mr Suddern, seems out of place. Huston, his business partner, is suave with an air of mystery. Colin takes a bus ride with Mary, ending up at London zoo. She tells him of growing up in the Belgian Congo, and of her strange relationship with Huston. Could there be blackmail involved? When Huston demands Colin give up his room, and an eminent physician comes to dinner, the truth behind the Adelaide man and Huston is revealed.
