NCIS “Oil and Water” began with a literal bang on a coastguard vessel, following last week's murder investigation centering around members of the U.S. armed forces and a Russian mobster.

While the blast occurs onboard the vessel, back at the office McGee and Abby (Pauley Perrette) realize they’re the victims of some office hijinks. McGee’s (Sean Murray) desk is clothed in plastic wrap, while the detail-oriented Abby’s desk has been shifted ever so slightly to the right. Tony (Michael Weatherly) is the prime pranking suspect, as even Gibbs (Mark Harmon) lets McGee know that Tony had stayed late at the office the night prior.

Teaming up with the Coast Guard Investigative Service, Special Agent Abigail Borin (Diane Neal) is their point person on the case. She informs the NCIS team that a marine has died due to an explosion on an off-shore oil platform. Unfortunately, they can’t take a good look at the crime scene, as there’s a fear that the platform could give way.

While Tony and McGee begin questioning the 50-odd witnesses, Borin pries Gibbs for the details surrounding Ziva’s (Cote de Pablo) departure from NCIS. Sidestepping her inquiries, Gibbs presses on about Marv Hebner, the Marine who died in the explosion. Tony learns from operations officer Jonah McGuire that he couldn’t believe for a second that the explosion was a result of carelessness on Hebner’s part. Through questioning, NCIS finds out that a cargo freighter witnessed a motor boot creeping near the platform the previous night.

For now, Homeland Security isn’t taking any chances with similar attacks and labels the hit on the oil platform as terrorist activity. Gibbs ends up having to attend a meeting with Secretary of the Navy Porter and City Line Oil. In the meeting he finds out that Mr. Creevy, the CEO and City Line lead counsel, had been able to peruse the platform the morning of the explosion. As for Borin, she finds out from Ducky – who has a mysterious beeping sound emanating from his office – that the Marine likely died via drowing after suffering a blow to the head.

Hard at work on the case, Abby figures out that someone remotely hacked into the oil rig’s systems. The hacker, uncovered by McGee and Tony, is student and activist Danielle Benton. Danielle claims that the program was solely a theoretical thesis project and would have been incapable of causing an explosion. After speaking with Creevy, Gibbs and Borin are led to believe that City Line’s Jonah McGuire may have intentionally targeted his coworker Hebner over a dispute.

Another twist – discovered by Abbie – is that the bomb was placed strategically in a location where it would not cause extensive damage to the rest of the rig or to people. The team goes on another chase after a food service employee. It’s another dead end. Eventually they’re led back to Danielle Benton. She too maintains her innocence, claiming that while she’s a protestor, she’s not about to blow anything up.

Another Abby discovery – leather and metal shrapnel from a suitcase – leads the NCIS team to their next and final suspect – Creevy. The lawyer apparently decided to cause the explosion in an attempt to make money after selling his City Line stock. He makes a full confession of his crimes. Case closed. As for the NCIS HQ prankster, it looks like it just might be Gibbs.

NCIS airs Tuesdays on CBS at 8/7c.

– Chelsea Regan

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