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 mountain home into Rockscar City to sell flavoured ices to the rich and dispense free, clean drinking water to the poor. But that was before the night the Ice Angel was found on the mountain road, mysteriously abandoned, and Balthazar 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 - Scarspring Water Company, headed by the ruthless Anshelm Scarspring, punishes anyone dispensing water. Is there a link with the mystery of their dad's disappearance? And what of Anshelm's obsession with the great wilderness beyond the city, with legends of troll who inhabit it, and with secret maps...Then drought hits Rockscar City: water supplies are polluted and dry up. Protests and riots brew against the Scarspring Water Company. And everything Zack and Clovis believed about their father and mother begins to unravel ...