When Callum and his friends find Iona on Callum's farm they try to chase her back into the village. But Iona runs from them up into the hills. It is late and dark and snow lies in the mountain gullies. Worried for Iona's safety, Callum follows to find her shivering with cold but refusing to leave. She is guarding a secret hidden in the forest above the dark waters of the loch. So they make a deal. Iona shares the secret and in return Callum allows her back onto the farm. They form a deep bond of friendship and make a promise to keep their secret safe from harm. It is a promise that will change Callum's world for ever ...