Dale McGarrigle

On Criminal Minds Season 13 Episode 18, Rossi gets a visit from his ex-wife, and the BAU heads to Chicago to investigate an unsub leaving roses on each victim.

On NCIS: New Orleans Season 4 Episode 18, Pride is personally requested by a former colleague to assist with a classified operation that has been compromised.

On The Alienist Season 1 Episode 10, Kreizler confronts the demons of his past, Moore tells Sara the truth, and the team closes in on the killer as time is running out.

On NCIS: Los Angeles Season 9 Episode 16, Callen pursues every option when his father is apprehended in an exchange of two Americans being held hostage in Iran.

On Timeless Season 2 Episode 3, Lucy, Wyatt and Rufus work with Hedy Lamarr to get the only copy of "Citizen Kane" back from a Rittenhouse sleeper agent in 1941.

As The Alienist Season 1 Episode 10 approaches, actor Daniel Bruhl talks about his character, Laszlo Kreisler, and the investigation for a killer which Kreizler has headed.

On Criminal Minds Season 13 Episode 17, when a murderous clown terrorizes the sleepy town of Guymon, Oklahoma, the BAU is called in to investigate.

On The Alienist Season 1 Episode 9, Kreizler mourns the loss of a friend, while Sara pushes the team to forge ahead and Moore warns Kreizler the killer will strike again.

On NCIS: Los Angeles Season 9 Episode 15, Callen and Sam pull Granger's daughter from witness protection to help the team locate an underground spy.

The Lifeboat crew jumps back to the 1950s, where Wyatt learns that his favorite stock-car driver is a Rittenhouse sleeper agent out to destroy the American car industry.

On Criminal Minds Season 13 Episode 16, the BAU meets in secret to investigate an UnSub who appears to be kidnapping and photographing young women.

On NCIS: New Orleans Season 4 Episode 17, the team investigates the murder of a Navy captain who was searching for a 200-year-old marble and gold fleur-de-lis.

On The Alienist Season 1 Episode 8, Sara goes rogue in pursuit of the truth, while Byrnes and Connor tighten their grip on the investigation.

On NCIS: Los Angeles Season 9 Episode 14, the team heads off on a dangerous and off-the-books rescue mission to save Hetty from her captors in Vietnam.

On Timeless Season 2 Episode 1, Wyatt and Rufus chase the Mothership back to a French battlefront during World War One to rescue Lucy from Rittenhouse.

On Hawaii Five-0 Season 6 Episode 17, Adam's mission to take down organized crime goes sideways when deadly chlorine gas falls into the wrong hands.

On NCIS: Los Angeles Season 9 Episode 14, the NCIS team, supplemented by Hetty's wartime comrades, head to Vietnam for a dangerous, off-the-books rescue operation.

On Criminal Minds Season 13 Episode 15, when the BAU investigates a quadruple homicide, they are joined by the FBI's Asst. Director of National Security.

On NCIS: New Orleans Season 4 Episode 16, the team investigates when a Congressional aide goes missing after a hitman saves her from men posing as NCIS agents.

On The Alienist Season 1 Episode 7, Kreizler and Moore follow a lead, Sara visits a hospital and is forced to confront her past and Cyrus recovers from his wounds.

On Hawaii Five-0 Season 8 Episode 16, Tani and Junior go undercover as prospective parents in order to infiltrate a private school whose headmaster is murdered.

On NCIS: New Orleans Season 4 Episode 15, Percy goes undercover as a getaway driver during an opioids theft investigation for FBI Special Agent Raymond Isler.

On The Alienist Season 1 Episode 6, the team hatches a plan to catch the killer, while Kreizler faces his own self-doubt about the investigation.

Some series neatly transition from cast to cast, while others implode when a key cast member departs. The secret to keep a series running is to make changes feel organic.