'NCIS' Season 13 episode 19 spoilers: ‘Reasonable Doubts’ pits wife vs mistress; plus Tony DiNozzo may have a sister

“NCIS” returns with a brand new episode on Tuesday, delivering another intriguing case that will test the team’s skills and shrewdness. The upcoming installment, titled “Reasonable Doubts,” centres on the murder case of a navy officer, which leads to a blaming game between his wife and his mistress. The episode also explores the possibility of Agent Anthony DiNozzo (Michael Weatherly) having a biological sibling.

Veteran actor Robert Wagner has signed up as a guest star for the March 22 run, reprising his role as Anthony DiNozzo Sr. He joins other “NCIS” cast members who will appear on the episode including Leroy Jethro Gibbs (Mark Harmon), Timothy McGee (Sean Murray), Eleanor Bishop (Emily Wickersham) and Jimmy Palmer (Brian Dietzen). Jon Cryer appears on the upcoming episode as Dr Cyril Taft, Leon Vance (Rocky Carroll), Abby Sciuto (Pauley Perrette) and Dr Donald Mallard (David McCallum).

Spoiler alert! This update contains more "NCIS Season 13" spoilers. Read on at your own risk if you have not watched the latest episode.

TV Guide reports that on Tuesday’s episode, Tony DiNozzo’s father lends a hand on a homeless woman who believes she is his lost daughter. Meanwhile, the team investigates the case of a Navy Public Affairs officer, who gets shot and killed. His wife and mistress are quick to point the finger at each other as the murderer.

“NCIS” also posted sneak peeks of its March 22 episode on its YouTube page. In one preview video, the team is shown facing a “she said, she said” challenge. They debate whether the true killer is the murder victim’s wife or his mistress. Dr Mallard succinctly puts it, “Scorned wife, or jilted lover?” As the crew throws off their theories, Gibbs replies, “We have varied opinions.”

Meanwhile, DiNozzo is seen walking with his dad when a woman approaches them, saying, “Dad, I’ve been looking all over for you.” DiNozzo asks his father if he has a sister that he doesn’t know about. The trailer wraps as the older DiNozzo knocks on Tony’s door, asking for his help. The camera pans to the homeless woman, who arrives with Tony’s father.

Fans are counting down the days before DiNozzo’s character, played by Weatherly, exits the highly popular series. They are wondering whether Ziva David (Cote de Pablo) appears on DiNozzo’s final episodes. While CBS is keeping mum about it, the show’s executive producer Gary Glasberg hints that there are big surprises on the way.

"People can absolutely plan on lots of surprises and lots of emotion, and lots of twists and turns, ultimately leading us toward Tony's departure," he tells TV Guide. "I promise you that everything you're fishing for will be delivered in some form." The finale will be aired on May 17.

Until then, fans are gearing up to see the March 22 episode of “NCIS,” which is directed by Thomas J. Wright, according to the Internet Movie Database, or IMDb. Find out what happens next on “NCIS” Season 13, which airs in the US on CBS every Tuesdays, 8/7c.