Aboard Air Force One a Naval officer dies after eating with the Potus, then a Marine officer (connected with AF1) also dies in Georgetown in the same way. Abby identifies the cause, and Gibbs thwarts an attempt to assassinate the PotUS.
During a training jump a Marine dies when his main chute fails to open, and he fails to pull his reserve chute. Kate joins the NCIS team, and they investigate; they identify not only the murderer and his method but also a drug connection.