The latest episode of NCIS Season 23 brought back a familiar face while putting the team in a dark and dangerous situation. Episode 17, titled Reboot, aired on Tuesday, April 21, 2026, and delivered a tense story that ended with a shocking cliffhanger. The episode focused on a late-night technology upgrade that turned into a deadly crime scene inside the NCIS headquarters. Viewers saw special agent Alden Parker (Gary Cole) team up with returning character Sam Hanna (LL Cool J) to solve the murder of a young tech expert while trapped in a powerless building.
Here is a complete breakdown of the cast and characters who brought this gripping episode to life.
Gary Cole as Alden Parker
Gary Cole continues to lead the team as Supervisory Special Agent Alden Parker. In Episode 17, Parker takes charge when a routine system reboot turns into a murder investigation. He is the one who finds Sam Hanna sleeping in the multi-purpose room during a layover. Parker immediately asks Sam to help hunt for the intruder hiding in the dark hallways. Cole has been a series regular since Season 19, and his character continues to show strong leadership skills during high-pressure moments.
LL Cool J as Sam Hanna
Music legend and actor LL Cool J returns as Sam Hanna in a special guest appearance. This marks his return to the NCIS universe before he officially leads the upcoming spin-off show, NCIS: New York, which is scheduled to join the CBS lineup in fall 2026. In this episode, Sam’s flight gets delayed. Instead of paying for a hotel, he decides to rest at the Navy Yard. He wakes up to find the building in chaos and immediately joins Parker and Jimmy Palmer in solving the case. His presence not only helps the team but also teases his future move to New York.
“Tell you what, we replace old MTAC with new MTAC, but people, like Vance… No replacing that.” – Sam Hanna reflects on the loss of Director Vance.
Diona Reasonover as Kasie Hines
Diona Reasonover plays forensic scientist Kasie Hines, who is at the center of this episode. Kasie decides to work late on a Sunday night to perform a two-hour system reboot to avoid daytime disruptions. She hires a group of “tech trolls” to help her. When the reboot fails and a murder occurs, Kasie tries to keep it a secret from her bosses. She ends up being the main target of the episode’s villain. The final scene reveals that a personal program she created, labeled “Edna,” was stolen from her laptop. Kasie admits, “I think I’m the reason why Daryl’s dead.”
Brian Dietzen as Jimmy Palmer
Chief Medical Examiner Jimmy Palmer, played by Brian Dietzen, gets several important moments in Episode 17. He teams up with Parker and Sam to solve the case. The episode also explores his personal life. Jimmy reveals to Sam that he has been training to climb Mount Kilimanjaro. To prove his fitness, Jimmy climbs up an elevator shaft when the team gets stuck. Sam encourages him to share his goal with the rest of the team, showing the strong friendship between the two characters.
Wilmer Valderrama and Katrina Law as Nick Torres and Jessica Knight
Wilmer Valderrama and Katrina Law appear as Special Agents Nick Torres and Jessica Knight. While the main action focuses on Parker, Kasie, and Sam, Torres and Knight are present during the investigation. They help interrogate the tech trolls and search for the missing plumber. Their roles in this episode are supportive, helping to move the plot forward as part of the skeleton crew trapped during the blackout.
Sean Murray as Timothy McGee
Sean Murray returns as Timothy McGee, the senior field agent. McGee is one of the key members of the team involved in the lockdown protocol when the killer is discovered inside the building. He helps manage the situation from the command center and assists in tracking down the hostage family.
Guest Stars in NCIS Season 23 Episode 17
The episode features several notable guest stars who play crucial roles in the story:
- Josh Sussman as Daryl Greco: A tech troll who is murdered inside the NCIS headquarters at the start of the episode.
- Geoffrey Arend as Tommy: The building janitor whose family is taken hostage. He is blackmailed into helping the real culprit.
- Noah Bean as DOD Chief Davis Barbado: A Department of Defense official who threatens Kasie if the MTAC upgrade fails.
- Josh Banday as Harold Goodell (aka Frank): A college friend of Daryl who faked his identity to get a job with NCIS.
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How to Watch NCIS Season 23 Episode 17
Episode 17 aired on Tuesday, April 21, 2026, at 8:00 PM Eastern Time on CBS. For viewers on the West Coast, the episode aired at 8:00 PM Pacific Time. Paramount+ Premium subscribers could watch the episode live as it aired. Paramount+ Essential subscribers can stream it the day after, starting April 22. In Canada, the episode airs on CBS or Global TV at the same time. In Australia, the episode is available to stream on Paramount+ Australia starting April 22. In the United Kingdom and India, the episode became available for streaming on April 22.
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