Nicola Long is a few years out of a fine arts degree, listless and unenthusiastically employed in London. She begins to spend her hours at a small underfunded archive dedicated to women's art. There she discovers one side of a correspondence beginning in 1976 and spanning a dozen years, written from one woman - a ceramics graduate, uncannily like Nicola - to a friend living a contrasting and conventionally moored life. As Nicola reads on, an acute sense of affinity turns into obsession.

She abandons one job after another to make time for the archive. The litany of coincidences in the letters becomes uncanny, and Nicola's feeling of ownership begets a growing dread: should she be afraid of where these letters are leading?