First Look: Masked Motives On NCIS

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

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

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

"Viral" (Season 13, Episode 6)
Kelli Williams as NCIS Special Agent Maureen Cabot and Pauley Perrette as Abby Sciuto

Kelli Williams as NCIS Special Agent Maureen Cabot and Pauley Perrette as Abby Sciuto

"Viral" (Season 13, Episode 6)
Pauley Perrette as Abby Sciuto

Pauley Perrette as Abby Sciuto

"Viral" (Season 13, Episode 6)
Kelli Williams as NCIS Special Agent Maureen Cabot, Mark Harmon as Leroy Jethro Gibbs, and Kelly Frye as Navy Lieutenant Kara Gifford

Kelli Williams as NCIS Special Agent Maureen Cabot, Mark Harmon as Leroy Jethro Gibbs, and Kelly Frye as Navy Lieutenant Kara Gifford

"Viral" (Season 13, Episode 6)
Emily Wickersham as Ellie Bishop, Mark Harmon as Leroy Jethro Gibbs, and Sean Murray as Timothy McGee

Emily Wickersham as Ellie Bishop, Mark Harmon as Leroy Jethro Gibbs, and Sean Murray as Timothy McGee

"Viral" (Season 13, Episode 6)
David McCallum as Donald

David McCallum as Donald "Ducky" Mallard, Sean Murray as Timothy McGee, Emily Wickersham as Ellie Bishop, and Mark Harmon as Leroy Jethro Gibbs

"Viral" (Season 13, Episode 6)
Emily Wickersham as Ellie Bishop, Mark Harmon as Leroy Jethro Gibbs, and Sean Murray as Timothy McGee

Emily Wickersham as Ellie Bishop, Mark Harmon as Leroy Jethro Gibbs, and Sean Murray as Timothy McGee

"Viral" (Season 13, Episode 6)
Emily Wickersham as Ellie Bishop

Emily Wickersham as Ellie Bishop

"Viral" (Season 13, Episode 6)