While investigating a mysterious death on a top-secret naval research ship at sea, the NCIS team comes upon an abandoned ship which contains a deadly secret that may cost them their lives.

When a dog owner is found murdered, the NCIS team must determine if his dog committed the murder or not, and Abby decides to fight for the dog's life by trusting her instinct about the dog's innocence. Meanwhile, Gibbs learns about Jenny's secret.

Demons of the past come back to haunt Gibbs when he finds a cryptic message waiting for him at a crime scene.

When a young boy finds a murder weapon, the team must trace ownership of the gun to find who used it last and who was murdered.