When a Marine falls ill during a training mission due to an attack by a genetic weapon, the NCIS must track down the person responsible for unleashing it. Also, Deeks struggles with balancing work and home life when Rosa comes down with the flu.

Bobby Hogan, Cyrus Hobbi, Dominic Burgess, Jesse Boone, Marcus Antony Brunner, Natalia Del Riego, Pamela Reed, Piper Curda, Susan Slome