The fourth season opens with the death of a Syrian informant and two FBI agents during a bomb blast. A former officer, a federal prisoner convicted of murder and robbery of the bank, Gibbs returns indefinitely and a real estate agent discovers the disintegrating body of the Navy. On the other hand, new investigations are being opened on Halloween, where the Gibbs team is investigating a Marine wounded by gunshots, In addition to kidnapping his daughter and asked for a financial amount of $ 100,000 in order to return her.