First Look: Masked Motives On NCIS

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Pauley Perrette as Abby Sciuto and Mark Harmon as Leroy Jethro Gibbs

On NCIS's "Viral" (Season 13, Episode 6), a petty officer's murder matches the M.O. of a local serial killer, forcing the NCIS team to determine if this is the killer's latest victim or the work of a copycat.