'NCIS' Season 11 Episode 17 Spoilers: Team Investigates Bomb That Detonates at a Concert

"NCIS" celebrated its 250th episode by bringing back Tony's father, who kept a secret from his son.

In "Dressed to Kill," Tony (Michael Weatherly) sees a man impersonating a Navy officer, and shoots and kills him in an alley, with his father (guest star Robert Wagner) as the sole witness. It turns out that the man who he shot had just come from shooting someone else.

The man was a private investigator, whose trail leads to the senator's secretary, who is very upset about the man's death.

It's discovered that the secretary was dating the P.I., and the investigator was dressed as a Navy officer because the man he shot was expecting to meet a Navy officer to analyze ports. The secret meeting had to do with a bill the senator was waiting to get passed.

Meanwhile, Tony's father says he has "great news" to share with his son, but keeps putting off telling him what the news is. Instead, he tells Tony that he's getting married again, but doesn't tell him anything about his fiancee.

Yet, during the murder investigation, Tony and Bishop (Emily Wickersham) see Tony's father going into a hotel room with a young pregnant woman.

After a lot of speculation, it turns out the pregnant woman is his fiancee's daughter. McGee Senior tells his son that his fiance is Linda, Tony's godmother and his mother's best friend. He insists that they did not have an affair while his mother was alive, but Tony still struggles with the news.

Tony tells Gibbs (Mark Harmon) that he feels like his father is betraying his mother, but Gibbs tells him that his father must feel the same way, and that's why he needs his approval about the impending marriage. Tony then gives his father his approval, and the two reconcile.

On the next episode, "Rock and a Hard Place," "After a bomb detonates in the dressing room at a military charity concert, the NCIS team must determine if the target was a washed-up '80s rocker or if the bomb was part of a larger scheme. Meanwhile, Jimmy prepares for fatherhood."

"Rock and a Hard Place" airs Tuesday, March 18, at 8 p.m. EST on CBS.