13 months after the events of the first season. A coastal tanker leaves the Oresund waterway and is headed straight for the Oresund Bridge. When the coastguard board the ship they discover there is no crew and three Swedish and two Danish youths are chainedbelow deck. Saga Noren of Malmo County Police is put in charge of the case and contacts Martin Rohde, who is still haunted by the death of his son. Together they embark on investigating the case.
While Saga and Martin are quarantined, someone posts a video online where four individuals wearing masks use signs to claim responsibility for the plague. This coincides with several reported deaths as a result of eating, among other things, poisoned apples. Saga and Martin are quick to connect the two cases. And they realise this is just the beginning.
Saga and Martin continue hunting down the eco-terrorists and start profiling them. The eco-terrorists now know the police are onto them and realise they will have to proceed with great caution as they go forward, hoping to be trusted with new and bigger operations. But there is a split in the group and Saga and Martin are edging closer. It dawns on Saga’s boyfriend Jacob that living with her isn’t entirely easy. Martin makes some progress in his meeting with Jens, but will Jens ever show remorse?
Saga and Martin investigate the killing of the eco-terrorists. Saga rules out suicide. They learn there must be a leader still alive out there who has been pulling the strings all along. They track him to a Copenhagen-based IT company, but he seems to have gone underground. Are new attacks being planned? Are there more terrorist cells? Martin hits it off with his Danish colleague Pernille, but is it more than just friendship?
As the investigation grows, some new leads are opened and four individuals wearing animal masks carry out a new attack and then post a video online where they again claim responsibility. Saga and Martin try to track down the new group, who are busy planning yet another attack. Saga has a hard time getting used to living with her boyfriend and feels she needs to be alone. She decides to check into a hotel, a decision she will soon come to regret. Martin goes back to visit Jens in prison and this time he exceeds his authority.
Martin is at the hospital watching over his son Nikolaj, who has suddenly fallen ill. Saga visits the hospital to update him on the case and notices that something isn’t quite right. The investigation intensifies as another poisoning is connected to Saga and Martin’s case. Furthermore, a motorboat is recovered from the bottom of the sea and some old skeletal remains are found inside. Who were these people and what did they die of? Are they connected to the larger case?
Saga and Martin face a complex puzzle when someone threatens to blow up a chemical plant. They collect all the clues and find a common denominator, confining the perpetrator to a specific area. But is there a single perpetrator or several? And what is the motive? Saga starts to realize that being a girlfriend and living with someone is harder than she thought. Martin has secretly been prying into Saga’s past, something he may regret.
Saga and Martin re-interview witnesses in the case and suspect someone within their own group has been doctoring information in their reports. But they need to gather more evidence before they can be sure. Laura, the key witness, regains consciousness and, despite feeling exhausted, finally manages to help piece together a composite sketch of the perpetrator.
After a composite sketch of the perpetrator is made and Saga and Martin learn who it is, they must get to him in time. When they think the case is solved, it turns out there is one more final piece left. Their leads point to Kastrup Airport, but once they realise what it all means it may be too late.
Saga and Martin realise the case isn’t over and that there is one more perpetrator. But who is Mikkel Host? It’s a race against the clock to prevent a disaster in which many lives are at stake. Martin makes a crucial decision, and in the end Saga faces an extremely difficult choice that will change everything.