"Navy CIS" stands for "Naval Criminal Investigative Service". The team of special agents is tasked with investigating crimes involving members of the US Navy or Marine Corps.
After the cliffhanger finale of season 19, Special Agent Alden Parker is still on the run while the NCIS team looks for ways to clear his name. With the help of NCIS: Hawaii special agents, the team finally manages to track down the prime suspect.
Season 20 of NCIS offers plenty of intriguing cases, plus a deeper look into the agents' personal lives.