The NCIS: Los Angeles cast will end their summer hiatus on Monday as they return to set to film "Inelegant Heart."

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Penned by R. Scott Gemmill and directed by executive producer John Peter Kousakis, the episode will mark the start of season 6 production.

"Last day of prep on E601!" Kousakis tweeted on Friday. "Let's get this party started. Production begins Monday."

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Although "Inelegant Heart" will be the first episode to film post-hiatus, the story will actually air the week after the season 6 premiere, "Deep Trouble: Part 2," which was shot last spring.

Little is known about the plot of "Inelegant Heart," but it will feature at least one scene down by the LA River (see photo here).

When Callen (Chris O'Donnell), Kensi (Daniela Ruah), Sam (LL Cool J), and Deeks (Eric Christian Olsen) do return to screens in "Deep Trouble: Part 2," the special operations team will be separated as Sam and Callen attempt to escape an explosive submarine while Deeks and Kensi take to the skies to find them.

Find out more when NCIS: LA airs Sept. 29 at 10 p.m. ET on CBS. Click the video below to see a preview of the series' latest episode.

Tags: NCIS: LA television CBS