Olly & the Spores of Sapphire Creek (Book 2)

Book 2 of the series: Olly Appleton thought he had learned all of his grandfather’s secrets, the ones his grandfather died protecting. Those secrets involved hand-drawn maps, special keys, hidden tunnels, and the Spores—friendly and fantastical mushroom creatures living under his home on Oak Hill. When Olly and Ember learn of a new secret, a new Spore community in an abandoned gold mine, they decide to visit. Together with the Spores and a few unlikely friends, they try to find the source of a toxin poisoning some of the Spores.