When military grade technology is stolen, a deaf engineer, Sienna Marchione, who always wanted to serve her country, and the only member of her team to survive the theft, helps Kensi and NCIS track down the tech before it's taken out of the country.

Deeks is kidnapped by an associate of Kirkin's who is in need of his help. Also, NCIS investigates the shooting of a militarized dolphin equipped with a Russian microchip and Beale makes Nell an interesting offer.