Dept Q Episode 9 Recap & Ending Explained: The Past And The Present Of The Hyperbaric Chamber

The final episode of Dept Q navigates through multiple psychological layers—past and present—and reaches a conclusion that is a sore spot. In a sense, what we are about to find out in this episode is a tragedy of errors that killed Sam Haig. It also subsequently displaces him from being the central figure who was either “helping” or “hurting” Merritt and reduces him to just a cameo. It is because Sam Haig was just a placeholder whose identity was being impersonated by Lyle Jennings to exact revenge on Merritt Lingard.

Spoilers Ahead

Carl, Rose, and Akram go to Godhaven, the juvenile facility where Sam had stayed. Terry Dundee reveals that Sam was a menace as a child—he was put into the facility for sleeping with his high school teacher and getting her debit card PIN. However, Lyle Jennings was also Sam’s contemporary in the facility. The two had gotten into a tiff since Lyle had developed a hyperfixation on Sam, thinking Sam is his brother Harry given the strange resemblance Sam bears to both the siblings. By that time, Harry was dead. They watch a tape of Lyle Jennings where Lyle reveals about his childhood after the death of his father, his mother Ailsa’s unconventional way of treating her sons, and how Harry has lived on even after death. Lyle’s singular aim is to protect Harry in his life. We also get to the bottom of Sam’s death. Sam had returned to Godhaven to write a book on his stay and also to possibly focus on Lyle; Lyle uses his guilt of hitting him in the past to teach him about manipulation tactics, which he used on Merritt, then pushed him off the Cullen Crag before the night that Merritt disappeared. It is unclear how he got to know about Sam’s whereabouts on that specific day, but for the benefit of our doubts, Sam did mention Cullen Crag and his climbing hobby to Lyle.

P.C. Cunningham visits Ailsa at home after the failed emergency call and finds his way into the hyperbaric chamber. The reason for his ambiguous position becomes clear now—he thought Lyle had pushed Merritt from the ferry to avenge his brother’s death; he says he wanted to put a peaceful end to this feud between two families, but he had no idea that Merritt was being kept in the hyperbaric chamber by the mother and son duo. Lyle does not give him the space for a dialogue and beats him brutally to death as Merritt watches. After the incident, Ailsa and Lyle are planning to leave, leaving Merritt to stifle and die as they set the pressure in the chamber to increase. 

William is brought into the office to identify Lyle Jennings, and with his nonverbal cues but unflinching love for his sister, William identifies the man in the cormorant hat to be Lyle. With the possibility of finding Lyle and to look into Cunningham’s disappearance, Carl and Akram head to Mhor one last time. While the duo is on their way, Hardy and Rose unearth information about Lyle’s troubled adolescent years after his father, Clive Jennings’s, death and his mother’s institutionalization for mental health, which spiraled into a series of ruthless crimes, including coercing a boy into the hyperbaric chamber where he and Harry would be punished. The chamber is on the property—Rose calls and informs Carl that Merritt Lingard may just be in one of the many chambers of the Shorebird Ocean System, which are cordoned off for hazardous material. They were declared as hazmat four years ago, strangely coinciding with Merritt’s disappearance. This is the strongest lead of the series, and it comes from Rose—what is truly commendable about Dept Q is that it is a story of many protagonists—all playing their roles in resolving the mystery of Merritt’s disappearance and, at the same time, being shaped by the currents of the flow. 

In Lyle Jenning’s tape, after getting a black eye from Sam Haig, we see a pathological portrait of what shaped him into the perpetrator that he became. Lyle mentions being locked up in a hyperbaric chamber with his brother Harry, and he also says that even after Harry’s death, Harry would always be in the chamber with him. Lyle protects Harry—this is the line behind his fixation. The LH inscription on the chamber’s wall is from their countless hours spent in the chamber, originally used for scuba divers to decompress after a particularly prolonged or deep dive. The chamber becomes a house of torture for the kids, implemented by Ailsa. There is a mention of Clive Jennings dying on his bed, burnt by a cigarette fire; however, Rose and Hardy have reason to believe that Lyle was involved in his father’s death. After Harry passed and Clive died, it may be Ailsa’s way of dealing with grief by maximizing the punishment and putting Lyle inside the chamber. Once she was sectioned for her mental health, Lyle had coerced a fifteen-year-old boy to be in the chamber and experimented to increase the pressure till the boy lost his senses, which was eventually discovered by the police. Hardy had commented after reading the file that Lyle was bent from his birth; he killed animals, showed no remorse, and had fixations of stalking multiple kids. This was worsened by the nurture from his mother and evidently became the worst when the mother’s repressed anger was directed at Lyle. Lyle became a living weapon and an open wound—ready to strike and then absorb Merritt into the unhealed parts of his psyche.The hyperbaric chamber is not symbolic of Merritt’s guilt; it is symbolic of how Lyle cannot escape his childhood trauma. He wants to replicate a victim; he wants to put someone in the position he once may have felt so helpless in and torture them the same way he was tortured. It is an act of justification and an idea of an absolute punishment. When the duo finds Merritt in the chamber, Lyle comes in and shoots Carl while Hardy is on call. A sly moment of poetic justice? However, Carl is barely brushed by the bullet, and Akram pulls a heroic stunt, killing Lyle in a sharp, swift movement. It is truly a team effort! However, extracting Merritt from the chamber would be impossible—the pressure is rising, and Merritt keeps hallucinating about her mother, her past, and everything else. She is almost on the verge of collapse; Hardy informs them that she can only be brought out by a hyperbaric stretcher, and the best thing they can do is to depressurize the chamber.

In certain ways, the depressurization feels symbolic of the trauma. A person like Lyle, living in the chamber of their own trauma, would not survive the outside world if they just stepped into it. The pressure would have to be stabilized, depressurized, in short—dealt with and healed. With another go at a team effort (yes, video meets are working out for the cops too!), They are successfully able to depressurize the chamber and rescue Merritt. It is a happy and fulfilling ending when William’s face appears over the stretcher and the siblings are reconciled.  Ailsa Jennings tries to escape but is stopped by officers. She shoots herself in the end, choosing submission after years of repression and misdirected rage. 

The series gives each of its characters a full arc, a praiseworthy screen time, and, not to say the least, soft endings. After Merritt is rescued, we look at her after three months. She visits Moira’s office, under the impression that Moira wanted to open her case (it was Akram!). As tongue-in-cheek humor as it can get about bosses and department chiefs! In the previous articles, we had often wondered about Merritt’s strong similarity with Carl; however, these are two stubborn, self-possessed, complicated creatures who stay parallel. Merritt only sees Carl one time, while she is stepping out of the elevator, a soft moment recognized only by Carl and not Merritt since she has no idea what Carl looks like.

Rose gets over her underconfidence as a desk officer and reestablishes her glory after playing a very crucial role in the investigation, and Hardy walks! He walks back into the office, and Moira assigns him to Dept. Q, probably to investigate the Anderson case, now that it’s taken off Clark’s hands. Carl came home to find Rachel waiting at his house with Jasper and Martin, and the three shared a tender, joyful moment. Carl also meets Stephen Burns and forgives him for what he did to save his daughter. But he also holds it as leverage to extract a double budget for the department, a car, and Akram’s promotion to being a DI. Nice work there, Carl. In the end, we see DCI Carl Morck sitting in the basement department, and he is joined by his friend, colleague, and partner James Hardy after all the hours on call, clearing any cloud that may have formed between them since the Leith Park Murder Case.For mystery investigation thrillers, Dept Q excels in its psychological depth, its ability to flesh out every character with their individual arcs, and the nuances of their interpersonal tendernesses. It is not just a whodunnit cop thriller but a slow, ambient observation of human nature—its guilts, consciences, and how that can shape human beings into being the heroes or the villains of their own stories. Dept Q is thematically heavy and introspective and would definitely overwhelm you by bringing a smile and a tear simultaneously to your face.