A "talisman-control failure" at the Tiangong Workshop Laboratory leaves a steam engine carving ancient inscriptions on its own before destroying itself. The inscriptions point to the "Key to the Wheel of Time: Lesser Key," missing for many years. Lin Yan and Su Jiu are forced to work together on the investigation. They discover that the Lesser Key is hidden in the cargo hold of an overseas merchant ship, which mysteriously sank three years ago on the edge of the Ruins Sea.
