Synopsis
While staying at the Scottish castle of his frail grandfather, a wild and peculiar adopted boy, Josh, learns of the legendary Silver Pearl which is rumoured to have healing power. Having recently been told that he is adopted, Josh’s unpredictable behaviour has driven his family nearly to distraction. When his grandfather has a sudden seizure, Josh secretly sets out to find the Pearl, and is followed by his younger sister Rose.
Guided by clues from their grandfather’s research, and pursued by their anxious parents - Greg and Anna - the children find a door to a secret passage which leads to the original resting place of the Silver Pearl. Here they are found by their parents, but also by two mysterious men, one of whom attacks, pushing them into an underground pool.
Josh rescues his family from the pool and they are housed by a mysterious fisherwoman named Maren who believes Josh is destined for great things. She reveals that the men hunting them are the dangerous water-horse beings from Scottish legend, known as Kelpies.
The next day, one of the Kelpies, Voran, finds Josh and confesses that he is his true father. He urges Josh to come home to live with the Kelpies. Josh refuses to believe it and so, to force the boy to follow him, Voran kidnaps Rose.
Josh, Greg and Anna pursue Voran to a loch, and in a cavern beneath it Josh discovers, to his relief, that Rose is safe. He also locates the Silver Pearl, but learns that it has been cursed by the oppressive Kelpie ruler, Karec, who Voran is plotting to overthrow. Voran promises the Pearl to Josh if he agrees to stay and help in the fight against Karec.
Meanwhile, Greg and Anna are distraught that Josh has abandoned them. They have a fierce argument and Greg leaves. Anna is about to despair when Maren appears and leads her to the cavern beneath the loch. After a soul-searching change of heart, Greg returns to follow them.
Just before Josh makes his vow to become a Kelpie forever, Anna and Greg arrive and chaos breaks out in the cavern. Josh manages to lift the curse from the Pearl, Karec is killed and the Kelpies are liberated. Keeping his promise, Voran gives the Pearl to Josh, and the family return home to heal Bert and return the Pearl to its rightful resting place.