Watch NCIS: Los Angeles Online: Season 9 Episode 21

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Who murdered a marine with nerve gas?

That was the big question on NCIS: Los Angeles Season 9 Episode 21 as the forensic investigation sent the team down various different avenues.

With that, NCIS and the FBI joined forces to find a way to take down the killer. 

However, it quickly became apparent that there could be more victims popping up along the way. 

Did the team find out all the details before it was too late?

Use the video above to watch NCIS: Los Angeles online right here via TV Fanatic. 

Get caught up with the latest action now. 

Paul Dailly is the Associate Editor for TV Fanatic. Follow him on Twitter.

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NCIS: Los Angeles Season 9 Episode 21 Quotes

Sam: You both need to learn to adapt.
Callen: The only way I'm going to learn to adapt is to buy a Fiat and learn to pout.
Sam: All you would need is the Fiat.

You need a reminder the world is coming to an end? I thought that's what Twitter is for.

Nell [to Eric]