In a small city shop, Maia practices the locksmith’s trade in a unique way: aided by an ancient power and a magical door, she can repair keys that hold extraordinary secrets. Accustomed to solving any puzzle with ease, she finds her skills challenged when a mysterious elderly woman hands her a broken key that defies every known technique. Just as she is about to give up, Maia discovers that the object does not respond to conventional methods and that the only way to repair it is to cross into the dimension hidden behind its own door.