Seven-year-old Luna is encouraged by her adoptive Aunt Maple to hide her unusual traits, especially as Luna is about to be taken, along with other children, to the Institution run by the tyrannical Archons; a Secret Society of otherworldly beings. There her true nature as the Moonchild is discovered, leading to terrible danger from which she escapes through a magical fireplace to another world. Pursued by Archons in this strange, fantastical world, Luna is rescued by pirate captain Harry Paye and his crew. From them she learns that her destiny is to return the Moonstone to Crystal Mountain before the approaching prophesied eclipse (Doomsday for both worlds). Facing many obstacles and dangers, Luna, aging by the day, perseveres, making friends along the way due to her kindness and compassion, but can she find and replace the Moonstone? And what secrets might she uncover as she pursues her quest?