While on Air Force One, a Navy Commander dies. Agents from the Navy NCIS decide to take the investigation into their own hands and force Secret Service Agent Kate Todd to help. The NCIS team then has to figure out if the Navy Officer's death was of natural causes or not.
After a robbery gone wrong ends with a murder and kidnapping, the team races to rescue a mother and daughter whose abductors are not what they seem; Crosby enters into a new living arrangement.
Danny and Baez try to prevent a gang war after a local mobster is discovered shot in his car. They only lead they have is an errand boy found in the boot.
The team investigate the weapon used in the murder of a scuba diver. Analysing the weapon found on the ocean floor they realise it was used in a another recent murder. McGarrett prepares to propose to Catherine.
Voight and the team muster all their expertise to bring down a deadly crime ring; Burgess finds herself in a dangerous situation.