With the sixth season premiere episode, Last Man Standing (episode), Rocky Carroll's name was added as a series regular and he was also added to the opening credits, even being given the credit "With", a credit he continues to hold to this day.
A body is found in the water system on a Marine Base is discovered. Ducky finds a note stuffed inside the victims mouth which leads to a website which shows how the first victim was killed. The team races to find the culprit because they know there will be more victims.
A bank at Quantico is robbed. As the team investigates they find that money may not have been the main objective. They must determine what the robbers were really after. Gibbs is asked to evaluate a new agent by the Director
Just 2 days before Christmas, a home invasion robbery leaves is linked to an old murder case. The suspect was identified as a petty officer who had died. NCIS tries to sort out what happened in time for the holiday
A sailor is murdered and the Agents quickly locate the 'suspect' and bring her back to the crime scene for identification. The Agents watch in horror as Ducky is stabbed at a crime scene - and they uncover a secret from Ducky's past that led to the attack
The team finds some numbers written in blood at crime scene. Gibbs instantly identifies the numbers as his, and knows it's a message for him. While the team tries to solve the murder, Gibbs calls his mentor Mike Franks in for help
A murder with a connection to an old case leads to a reversal of roles for Gibbs and DiNozzo. DiNozzo leads the team in the investigation linking the murder to an embezzlement scheme that sent an innocent man to prison.