Zack and Clovis are obsessed with the strange and unexplained disappearance of their father, Balthazar. Every night he used to drive his van, the Ice Angel, from the family's secret mountainside home into Rockscar City, selling flavoured ices to the rich and dispensing free, clean drinking water to the poor. But that was before the night the Ice Angel was found on the mountain road, abandoned, and Balthazaar never seen again ...Now, many years later, Zack and Clovis revive the Ice Angel and plan to carry on their dad's legacy, using the family's secret spring and old recipe book to create the most mouth-watering ices imaginable: crushed vanilla with ginger crystals, coffee and bitter chocolate with frozen crystallized orange spoons, and cherry and cream vanilla bombes. But great danger looms -- Silverspring Water Company, headed by the ruthless Anselm Silverspring, punishes anyone dispensing water. Is there a link with their dad's strange disappearance. And what of his obsession with the great wilderness beyond the city, and the legends of troll who inhabit it, and secret maps ...Then drought hits Rockscar City: water supplies are polluted and dry up. Protests and riots brew against the Silverspring Water Company. And everything Zack and Clovis believed about their father and mother, begins to unravel ...