Ms. Harbor has a fun new project for the purrmaids: a scavenger hunt. The purrmaids must search Kittentail Cove to find items around the ocean. Some are rare—like a special piece of coral. And some are too plentiful—like plastic human garbage. When Coral, Shelly, and Angel visit their mermicorn friend, Sirena, they discover that Sirena’s younger brother is caught in plastic soda rings. It’s up to the purrmaids to help their friend and clean up the ocean!