Ailsa takes a dislike to Calum Page from the day she is invited to play tennis with his sister. She knows Mrs Page looks down on her because her mother is the matron at Woburn Hostel, but Ailsa enjoys her life there. It's rich and varied and sometimes strange. In particular, she is fascinated with the love life of her glamorous roommate, Gloria. At first Gloria is amused when anonymous love letters start to arrive, but as each letter becomes more menacing both girls realise the writer knows Gloria's every move and must be watching her - day and night. When the stalker closes in on Gloria, Ailsa becomes convinced she knows his identity. As she struggles to understand the complexities of obsessive love, Ailsa finds an unexpected ally and a gentler kind of love.