A summer holiday and an old folk tale bring two 11-year-olds together as they set out to explore just what, or who, is calling to them, from deep within an abandoned tin mine.

11-year-old Evie arrives in Cornwall expecting a girls' holiday with her mum. But when she meets local boy Adam, a mysterious discovery down an old tin mine changes everything. As they begin to question what is real and imagined in their lives above ground, childhood narratives unravel and a darker, more complex picture of the adult world takes shape.