"NCIS" Season 11, Episode 5 ("Once a Crook") takes Tony DiNozzo (Michael Weatherly) back to 15 years ago, when he was just a cop newbie. He hasn't slept for days, and rants to Gibbs (Mark Harmon): 'It's like [Ziva David] is dead.' Meanwhile, Abby, forced to work with Delilah, now seems to like McGee's girlfriend.

Spoiler alert: This feature contains spoilers for those who have not seen "Once a Crook," NCIS Season 11, Episode 5.

Since Cote de Pablo left NCIS, the show has marked changes, starting from the Gibbs-DiNozzo-Ziva dynamics. Tumblr user @iheartstanak grieves the loss in this post. (CBS, NCIS on Tumblr.com)

Young Tony worked with a teen informant who later got caught by the bad guys. Despite not being able to sleep for days, present Tony manages to help his "old friend" reunite with his family. Gibbs helps him, of course. NCIS 11x05 shows Gibbs and DiNozzo in a couple of serious father-son moments.

Gibbs, visibly worried over Tony's less-than-sharp disposition, asks him mid-conversation: "Are we still talking about the case?"

"It's so interesting. No one will say her name. Have you noticed? It's like she's dead."

Ziva David (Cote de Pablo) was last seen in NCIS Season 11, Episode 2: "Past, Present, and Future." The next two episodes showed Gibbs' team working with a different female agent, but none was going to be Ziva's replacement. Roma Maffia's character was about to retire. Jackie Geary's Agent Grady was eyeing a promotion elsewhere.

Come November, Cote de Pablo's replacement (or potential replacement) will be introduced. NCIS showrunner Gary Glasberg describes Emily Wickersham in an interview.

NCIS Season 11 will soon introduce Ellie Bishop, to be portrayed by "Sopranos" star Emily Wickersham. In his TV Line report, Matt Mitovich said fans are thinking Ellie could be a female McGee.

"That was because there was a line that either I or someone threw out there, that described her in a specific way, as being... I forget what the phrase was. But she's not [like McGee]. Emily Wickersham is a terrific actress and she's going to bring a whole new spin and life to this character," Glasberg said.

Meanwhile, McGee (Sean Murray) is able to somewhat work with present and former girlfriends Delilah (Margo Harshman) and Abby (Pauley Perrette) to solve the team's case, which is related to Young Tony's case 15 years ago. Abby is reluctant to work with Delilah, but Gibbs needs them. Eventually, it seems the two have become good working friends.

NCIS Season 11, Episode 6 is called "Oil and Water." The series airs on CBS every Tuesday. The brilliant and lovely Leslie Hope will be back as Secnav Sarah Porter. This could be the last episode to show Ziva's desk as vacant. Glasberg's interview implies Cote de Pablo's replacement will arrive in November, but a specific episode was not announced.

More 'NCIS Season 11' and TV Guide Features:

NCIS Season 11 Spoilers: Mike Franks 'Returns' in Episode 4; Cote de Pablo Replacement is Emily Wickersham? [READ]
NCIS Season 11 Episode 2: Cote de Pablo Exits, Ziva David Kisses Tony Goodbye - For Now? [PHOTOS]