When a Navy sailor washes up dead in a sacred, forbidden kapu site, the NCIS team brings CGIS Special Agent Pike to unmask the mystery and catch a possible serial killer on the island. Also, Tennant meets Alex's new girlfriend.

When a Marine Corporal dies in a tide pool after being exposed to fentanyl, the NCIS team must quickly find the source of the drugs. Also, Alex talks to his parents about taking a gap year and Ernie reveals personal news to Lucy.