Merrilyn’s North Island friends are determined to help her and the other Sea Maidens vanquish sea monster Lord Pike. They have discovered a great deal, but little do they know the depth of the evil that lurks beneath the Cook Strait. Ginny, Chrissie and Emily are on the way as fast as they can get on board a ferry, but the precious heir to Marina they carry in his concrete enchanted form is the very being the true villain of the underwater world wants to get her hands on. The Sea Maidens are playing right into her eager talons and the merfolk are powerless to intercede.