An NCIS agent who used to work under Gibbs asks for the team's help investigating a case where sailors on an aircraft carrier are dying of a drug overdose, but have no history of any kind of drug abuse.

The NCIS investigation of a fire on a Navy vessel reveals evidence that elevates security at all U.S. Navy facilities worldwide. Meanwhile, DiNozzo and Ziva travel to Italy when an explosive device is found hidden on a Navy ship.

DiNozzo is reunited with his ex-girlfriend, Jeanne Benoit, when insurgents in Sudan attack a group of volunteer doctors, including her husband. DiNozzo and McGee travel to the crime scene for the joint murder and kidnapping case and join the search for the missing doctors.