Armand ignores repeated calls from his nemesis Jeanne Caron, then finally tells her to go to hell.

Armand's Montreal apartment is broken into and his raincoat is stolen during the break-in.

The stolen raincoat is delivered to Sûreté headquarters with two hidden notes found in the pockets.

A man named Charles Langois meets Armand at a café and warns him that the Sûreté is compromised.

An SUV deliberately strikes and kills Charles outside the café; Armand protects a young girl from the crash.

Armand holds Charles's hand as he dies; Charles's last word to Armand is 'family.'

Security footage at The Mission shelter shows Charles meeting with Jeanne Caron on multiple occasions.

Armand discovers that a monk named Dom Philippe left cryptic clues for him at the local B&B and church.

Armand and Jean-Guy travel by float plane through a dangerous storm to Dom Philippe's remote monastery.

Jean-Guy discovers Charles's annotated map hidden inside the monastery, marking polluted lakes across Quebec.

Armand visits the Rousseau family in Blanc-Sablon and learns that Jeanne Caron is Dom Philippe's niece.

RCMP agent Gauthier opens fire inside the Three Pines church and shoots Yves multiple times.

Armand holds Yves's hand as he dies; Jean-Guy handcuffs Gauthier to a church pew.

Inside the water-treatment plant, Armand switches the poison aspirin bottle for a bottle of Three Pines spring water.

Jeanne shoots David Lavigne as he fires at Armand, saving Armand's life and stopping the attack.

Armand Gamache's quiet morning in Three Pines is shattered when his Montreal apartment is broken into and his stolen raincoat is returned with cryptic notes, leading him to a clandestine meeting with a man named Charles Langois who warns him the Sûreté is compromised before being killed by a hit-and-run SUV. Following clues left by a monk he once knew, Dom Philippe, Armand pieces together a conspiracy to poison Montreal's water supply while quietly moving his family to safety. The investigation carries Armand from Montreal's streets to the remote monastery Saint Gilbert Between the Wolves, then to the fishing village of Blanc-Sablon, where he discovers a shocking family connection at the heart of the conspiracy. The climax unfolds in the Three Pines church, where a corrupt RCMP agent kills Philippe, and then inside a water-treatment plant where Armand risks his life to neutralize the poison. Armand barely survives, the attack is foiled, and the chief conspirators are brought down—but the cost is high and a new mystery is already taking shape.

The headline investigation into a plot to poison Montreal's drinking water.

Reine-Marie and her friends at the bistro learn the caller who made Armand curse was Jeanne Caron.

Jean-Guy interviews AQB director Margaux and learns Charles was a marine biologist investigating lake pollution.

Vlogger Shona publicly attacks Armand at a Sûreté news conference, accusing him of harming the young girl he saved.

Armand quietly invites his children's families to stay in Three Pines to drink safely from its well water.

Armand meets with RCMP Assistant Commissioner David Lavigne and shares his suspicions about the water supply threat.

The float plane carrying Armand and Jean-Guy nearly crashes during a violent storm on the way to the monastery.

Frere Simon reveals that Sebastien was appointed Dom Philippe's second-in-command before being summoned to Rome.

Jean-Guy meets former US General Whitehead in Washington to discuss the devastating consequences of a water supply attack.

British counterintelligence chief Sherry tells Armand that botulinum transported in an aspirin bottle is the most likely weapon.

Jean-Guy learns that Sebastien, Robert, and Irene were disciplined for singing karaoke while wearing their religious robes.

Isabelle travels to the Vatican and identifies Sister Irene, connecting her to the Washington seminary and to Sebastien.

Armand retrieves Dom Philippe's discarded chartreuse bottle from Olivier's recycling bin and confirms it was made in France.

Charles's parents finally admit that Charles left his notebooks with them and hand them over to Armand.

Isabelle and Claude discover Brother Robert's body at the base of a turret at Grande Chartreuse monastery.

Armand suffers hearing loss from being grazed by a bullet; Lauzon is later arrested using evidence Jeanne collected.

While Armand leads the investigation in Quebec, his team fans out across multiple countries to gather critical intelligence. Jean-Guy travels to Washington DC to meet General Whitehead and assess the catastrophic potential of a water attack, while Isabelle is dispatched first to Rome and then to France to track down monks connected to the chartreuse recipe and the conspiracy. Back in Canada, key evidence accumulates—from a discarded chartreuse bottle traced to a French monastery to Charles's hidden notebooks recovered from his estranged parents—as Armand navigates public attacks from the vlogger Shona and makes the dangerous decision to confide in the corrupt David Lavigne. Secondary figures including AQB director Margaux, British counterintelligence chief Sherry, and the monk Constantine each provide the pivotal pieces of information that allow Armand to close in on the truth. The pool ends with the aftermath of the attack: Armand heals from hearing loss, Lauzon is arrested using Jeanne's evidence, and the community quietly gathers around Armand in Three Pines.

The supporting investigations that built the case from Rome to Washington.

Armand spots a familiar face in Three Pines who is later revealed to be Dom Philippe dressed in plain clothes.

Armand catches Charles in a lie during the café meeting—Charles is a volunteer at The Mission, not a resident.

Jean-Guy identifies a button found in Charles's ransacked apartment as belonging to environmental group Action Quebec Bleu.

Armand shares his theory with Jean-Guy and Isabelle that someone is planning to poison Montreal's drinking water supply.

Frere Simon confesses to Armand that he secretly opened the Vatican letter sent to Sebastien and Philippe's letter too.

Armand tells Jean-Guy the Cree legend of two wolves fighting inside every person—one gray and good, one black and vengeful.

Armand learns from Philippe's seminary friend that the monk's birth name is Yves Rousseau, originally from Blanc-Sablon.

Armand meets with vlogger Shona and enlists her to investigate the government's pollution waivers and sale of water resources.

Isabelle realizes that Robert confided in Irene, Irene alerted Sebastien, and Sebastien then wrote to Dom Philippe.

Jean-Guy discovers that the Mission shelter regular called 'Big Stink' who befriended the SUV driver was Dom Philippe.

Armand holds Jeanne at gunpoint in the Three Pines church and she reveals which water-treatment plant will be targeted.

Monk Constantine shows Isabelle newspaper clippings proving the two earlier murders were contract killings meant to silence Robert.

Armand reads Charles's notebook and finds David Lavigne's name listed among the conspirators planning the attack.

Sebastien tells Isabelle that he views poisoning the water supply as justified ecoterrorism necessary to save the planet.

Armand realizes Charles's second notebook about lake pollution points to an entirely new unsolved conspiracy, ending the book on a cliffhanger.

This pool traces the moments of discovery and revelation that transformed the investigation, each one shifting Armand's understanding of who could be trusted and what was truly at stake. Early clues—a mysterious stranger spotted in Three Pines, a small lie told over coffee—gave way to larger revelations: a button linking Charles to an environmental group, a Cree legend about two wolves that named the moral stakes of the case, and the true identity of a monk who had been hiding behind a false name. As Armand's team spread across continents, they uncovered the chain of clergy who knew about the plot, traced the conspiracy to a corrupt politician, and discovered that Jeanne—Armand's longtime nemesis—had actually been working to stop the attack all along. The pool closes with the revelation of Charles's second notebook, a document about lake pollution that points to a deeper, unsolved conspiracy and leaves the story on a deliberate cliffhanger.