A Federal Agent is murdered in a shootout downtown and NCIS:LA is called in to track down the killer. Through street surveillance cameras, the team finds the agent was meeting a woman whose husband, a plastic surgeon, is also found dead. The woman, Jillian Leigh, is on the run and Callen and the team must find her. The team discovers that Leigh's husband was performing reconstructive surgery on known Al Qaeda terrorists. Kensi and Deeks go undercover and almost catch Jillian but she alludes them. They finally track her down at a former colleague's home and she tells them she knew nothing about her husband's involvement with these terrorists but Callen and Sam know she is the only one that can identify them. When material to make Sarin Gas is found in a storage unit linked to the group, the team knows the attack with be massive. They find the terror cell is planning an attack on the Queen Mary tonight and Sam convinces Jillian that she is the only one who can help the team save hundreds of lives. She agrees and Callen and the team go undercover at the Queen Mary event. The terrorists spot Jillian and know they must attack but our team chases the terrorists down and stops the catastrophic Sarin gas attack.