Sarah brings the alarming message on Katie's phone to the police, hoping it will push the investigation forward. Yet when she tries to show it again, the message has mysteriously disappeared. The uncertainty deepens doubts about what really happened the night Katie vanished.

As Captain Jerome Ricard and Lieutenant Virginie Taylor continue their inquiries, Sarah begins her own search through Saint-Michel. At a local bar she learns that Katie was seen on the night of her disappearance with Xavier and Emma Morvan, shortly before an incident that caused damage at a nearby hotel.

Determined to find answers, Sarah tracks Xavier to his isolated caravan outside town. Inside she discovers troubling signs of drug activity and traces of blood. When Xavier returns unexpectedly, the confrontation turns tense, but he insists Katie left alone after an argument with Emma.

Meanwhile, the investigation uncovers new evidence linking several students to the events of that night. Virginie's questioning of Emma raises further inconsistencies, especially after an item belonging to Katie is discovered hidden among Emma's belongings.

Tensions escalate between Sarah and the Morvan family, whose reactions grow increasingly defensive. The town itself seems divided - some residents sympathetic, others openly hostile to Sarah's relentless questioning.

Then a new development shocks the community: Katie's backpack suddenly appears in a public place connected to an older local tragedy.

Virginie reveals that another teenage girl disappeared in Saint-Michel five years earlier under eerily similar circumstances. As the parallels between the two cases begin to emerge, Sarah realises Katie's disappearance may be part of something far more complicated than anyone first believed.

In the aftermath of a shocking incident near the riverbank, the investigation into Katie's disappearance intensifies. The tragedy sends shockwaves through Saint-Michel and deepens Sarah's determination to uncover what really happened to her daughter.

Certain that the Morvan family is hiding something, Sarah openly accuses Fabien Morvan of being involved in the events surrounding Katie's disappearance. The accusation sparks conflict within the town, drawing increased media attention to the case.

As journalists begin arriving in Saint-Michel, Sarah publicly links Katie's disappearance to the earlier case of Odile Lambert, forcing local authorities to confront questions that have lingered for years.

Lieutenant Virginie Taylor begins digging deeper into both cases, revisiting old witness statements and investigating a suspicious vehicle that may have been seen the night Odile vanished. Her search begins to expose troubling gaps in the earlier investigation.

At the same time, Sarah receives a shocking new message that suggests Katie's story may not yet be over. The message sparks renewed urgency within the police inquiry, and Virginie works quickly to trace its origin.

Meanwhile, tensions grow among several people connected to the case as long-buried secrets threaten to surface. Relationships within the police force itself begin to strain as Virginie questions decisions made in the past.

A disturbing discovery soon leads investigators back into the woods, where they uncover evidence that could change the direction of the investigation.

As suspicion spreads through Saint-Michel and the list of possible suspects grows, Virginie begins to suspect that the truth about both disappearances may lie closer to home than anyone expected.