Phyllis Ewans, a prominent researcher in Lepidoptera and a keen walker, has died of old age. Thomas, a much younger fellow researcher of moths first met Phyllis when he was a child. He became her carer and companion, having rekindled her acquaintance in later life.

Increasingly possessed by thoughts that he somehow actually is Phyllis Ewans, and unable to rid himself of the feeling that she is haunting him, Thomas must discover her secrets through her many possessions and photographs, before he is lost permanently in a labyrinth of memories long past.

Steeped in dusty melancholy and analogue shadows, Mothlight is an uncanny story of grief, memory and the price of obsession.