Captivated by the allure of the sea, man has always been intrigued by underwater exploration and the mysteries of the deep. The year is 1873. Dundalk-based, noviciate Christian Brother, John Philip Holland is obsessed with his design for a bizarre, submergible craft. He soon finds himself caught up in the frantic, international race to tame 'the Mistress of the Sea'.
Infused with the inventiveness of the eccentric genius, this true-story drama tells the little-known tale of 'the father of the modern submarine' and one of Ireland's greatest, unsung naval heroes.