Catherine Bell Is Back as Mac in 'NCIS: LA' Finale: See a First Look (Exclusive)

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Catherine Bell is back as Mac.

After reuniting with JAG co-star David James Elliott earlier this season, Bell returns to NCIS: LA on Sunday to close out the season, and only ET has the exclusive first look at her return.

In the episode, titled "Code of Conduct," Sam (LL Cool J), Callen (Chris O'Donnell) and Rountree (guest star Caleb Castille) travel to Afghanistan when Marine Lt. Col. Sarah "Mac" MacKenzie (Bell) seeks out the help of NCIS to help with a sensitive case after two SEALs claim their chief murdered an unarmed prisoner.

In ET's exclusive clip, Mac enters Special Ops with Kensi (Daniela Ruah), Deeks (Eric Christian Olsen), Eric (Barrett Foa) and Fatima (Medallion Rahimi) to get the low-down on the dangerous task at hand. As the seconds tick by, things get more dire and as the team discovers, this latest mission isn't getting off on the right foot. 

“Catherine Bell’s character, Sarah 'Mac' MacKenzie, is back on NCIS: Los Angeles! Mac's been ordered to oversee our teams investigation into allegations that a Navy SEAL has murdered a prisoner in cold blood," executive producer Frank Military, who wrote and directed Sunday's episode, exclusively tells ET. "In this extremely dramatic season finale, not only do we get to have one of the show’s legacy characters back, (a legacy that goes back over 20 years to JAG!) but our cast and crew are always incredibly excited to be working with an actor as skilled and fun as Catherine.”

Back in September, Bell spoke with ET about the possibility of returning to the series.

"It became a full-circle moment. It seems to be something that people are really into, with all these shows that are coming back in different versions. We'd be the original cast; I mean, I think that'd be great," the Good Witch actress said at the time of being a more regular presence on NCIS: LA. "I'd be open to that. I think there were some great reaction. I know my fans are freaking out on Instagram about the possibility."

The NCIS: LA finale airs Sunday, April 26 at 10 p.m. ET/PT on CBS.

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