Mines That Explode Later (Than Expected)

A story of a ten year old girl, Erla, who finds a flute nobody else can hear and meets a boy nobody else can see. The boy turns out to be an elf who tells her that a spell has been cast on her father. Much to Erla's horror, her father is turned to stone when he's moving rocks around in the park, looking for worms. Erla's new found friend is the only one who can guide her on a search for a magic egg possessed by the big trolls in the mountains and said to be the only remedy for people who have been turned to stone.