NCIS: Los Angeles' Hetty isn't about to leave her agents, especially not when they are in mortal danger.

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Already in trouble with her superiors, the operations manager will choose to defy more orders in the season 6 premiere. The powers that be summoned Ms. Lange (Linda Hunt) to Washington during last spring's finale, but Hetty will change her travel plans in order to help save Sam (LL Cool J) and Callen (Chris O'Donnell).

Unfortunately, those two agents will wind up taking an unscheduled trip of their own during "Deep Trouble: Part Two." Trapped on a bomb-laden submarine, Sam and Callen will head down the coast to San Diego. Once there, the pair's terrorist co-passengers will attempt to steer their bomb towards a U.S. aircraft carrier.

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"We pick up where we left off last season," said Daniela Ruah (Kensi) on Extra. "Callen and Sam (played by Chris O'Donnell and LL Cool J) are in grave danger. They're stuck in this submarine and the whole team is trying to get to them and they're out of contact."

Find out more when NCIS: LA returns to CBS on Sept. 29 at 10 p.m. ET. Click the video below to see a preview for the series' latest episode, "Deep Trouble."

Tags: NCIS: LA NCIS: Los Angeles television CBS