When Katie Firestone, a friend of George Fayne, invites Nancy Drew to Deception Island for a whale-watching excursion, the sleuth arrives to find Katie's tour boat heavily vandalized. A threatening note was left behind that warns Katie to "stop meddling". Apparently, the residents of the harbor are divided over what to do with an orphaned female Orca whale that recently appeared in the channel, and Katie has ruffled a lot of feathers in the debate. Nancy must hunt down the vandal while unraveling some of Deception Island's hidden secrets.