A serial killer could be on the loose in the Season 13, Episode 6 showing of "NCIS."

CarterMatt reports as more and more of the details in a string of unsolved murders point to a distinct pattern, the gang must quickly determine if the latest slaying of a petty officer is indeed the gruesome work of a crazed murderer or if there might be a copycat also on the loose.

The "Viral" entitled episode also finds Delilah (Margo Harshman) and McGee (Sean Murray) faced with learning the art of compromise as they ready themselves to take the next step in their relationship by moving in together. The episode represents the work and vision of Leon Vance character Rocky Carroll, entrusted with directing his first episode since Season 12.

Thus far, much of this season has been about fans getting to see and experience a different side of the characters they've come to love. In the Episode 5 entitled "Lockdown" show, Abby (Pauley Perrette) exposed fans to another dimension of her range when she starred as the cast member left to negotiate the safe release of a bevy of hostages after they were taken at gunpoint by a crew of crazed assailants.

The whole season has been about getting to know a new and different Gibbs (Mark Harmon), as he struggles to find new perspective following his shooting and near-death experience that marked the climax of last season.

In the last episode, for the first time in what seems like forever, Gibbs found himself actively taking to the field, as he and Vance probed the puzzling death of a Navy Seamen Apprentice suspected of being involved in a convenience store robbery just before his death where he used a fake hand grenade as a weapon.

"NCIS" airs on CBS on Tuesday, Oct. 27, and also stars Michael Weatherly as Special Agent Anthony DiNozzo, Emily Wickersham as Ellie Bishop, Brian Dietzen as Jimmy Palmer and David McCallum as Dr. Mallard.