When a Naval Lieutenant who's current assignment is being the aide of an Admiral is found killed in the Admiral's office. The team goes to investigate and wonders why was he killed. Gibbs tells Tony who's been working non-stop for a few days to go home to rest. When he goes home he finds his father there and he tells Tony that the woman he was going to marry decided not to. When Abby examines the crime scene she thinks something is wrong. It's the painting where the Lieutenant died in front of. The painting is a masterpiece on loan to the Admiral but what is on the wall now is a forgery. So they think the Lieutenat was killed to get the painting. Question is how do they find the killers. Tony's father upon seeing they are looking for the painting says he dealt with people who deal in gray art, so they ask him to help them find who has the painting.