It's not unusual for twelve-year-old Alessia to lose control of her emotions and create a scene at school. It unusual when one day she's attacked there by a giant frog monster and plunged into the underwater realm of Atlantis in an overturned boat. On arriving in Atlantis, she learns that her long-lost father may have been from there. Determined to investigate, she stays and enrolls in Atlantide school: The Octopus's Garden. But uncovering the truth is not easy when the tyrannical Atlantide Emperor forbids asking about missing people. With the help of her newfound school friends, Alessia will have to steal evidence from a grumpy teacher, escape from rebel merfolk and make rhymes with menacing blue people of Minch to discover the key to her past. Meanwhile, someone knows exactly who she's the daughter of, and is ready to kill her for it.