After Julian Vance was locked up, Nora thought it was over. But new drowning cases surface—same method as Julian. The killer is a woman with a Seven-Ring Seal on her wrist. Nora and Ethan discover Julian was sending messages from prison through Morse code, training an apprentice—a guard named Lucas Crain. Lucas had his girlfriend Amanda do the killing on the outside. But behind it all is Julian's psychiatrist, Isabel Crayne—and a much older name. Corvus.