In a bloodthirsty episode, Saga begins to see the emerging pattern on the evidence wall, while the rising body count takes its toll on her partner Henrik

Spoiler alert: This is for people watching The Bridge at BBC Two pace. Don’t read on if you haven’t seen episode four of the fourth series – and if you’ve seen further ahead, please do not post spoilers.

You can read the previous recaps here.

To Saga, deaths – even avoidable ones – are data. By the end of a bloodthirsty episode in which a former prime suspect opted to take his own life and a bad dad was cruelly tricked into murdering his daughter, she had intuited a working theory to link the seemingly random killings filling up the Copenhagen evidence wall. For Saga, it is some sort of gift. But for her partner Henrik – so shaken by recent turns in the Margrethe Thormod stoning case that he sought out his old drug dealer – the rising body count is taking a toll.

We have a new suspect, at least. Morgan Sonning, owner of the black Audi that picked up Margrethe on the day of her death and a slick Stewart Lee haircut. Despite a tense late-night encounter with Taariq Shirazi, Sonning seemed unflappable, even smug, when questioned by police. He had a handy alibi for the night of the stoning: his car was getting worked on at his brother’s garage in Sweden while he and his wife, Malene, were on a (suspiciously cash-only, mobile-free) Hamburg city break. That did not stop Saga and Henrik kicking the tyres of his story as they nosed around his brother Tobias’s garage to see who else might have accessed the Audi.

The burning fuse throughout this episode took place almost entirely away from the main investigation. Arms dealer William Ramberg, who we had previously seen carrying himself with the menacing air of someone used to getting their own way, was dispatched on a berserk Malmö mercy mission that would not have felt out of place in a Saw movie. After receiving a video message portraying his daughter Leonora being injected with some mysterious yellow compound by the creepy clown from last week, William believed he only had four hours to raise a ransom and acquire the antidote (delivered by drone). The callous twist – that the antidote was a lethal neurotoxin, and that by injecting it he had killed Leonora – seemed to snap William’s sanity like a breadstick.

Poor Taariq. After slipping police surveillance in Copenhagen, he had ditched his wild hair, shaved off his beard and was making a desperate break for Sweden, only to be challenged by a diligent border guard. The resulting armed standoff ended swiftly and violently, but it seemed notable that even after only knowing Saga for a brief time, Taariq instinctively knew she would tell him the bald truth about his limited options rather than string him along with hostage negotiation tactics.

Seeing a man blow his brains out in front of you feels like something you might want to discuss with your therapist, but Saga’s latest session skipped over all that to burrow a little deeper into her knotty relationship with her parents. Her psychiatrist brightly encouraged Saga to analyse her feelings rather than rocket past them, and received a heroically furrowed brow in return. Even if she struggles to analyse her own emotions, Saga was still the only one able to see the emerging pattern on the evidence wall. Deaths by stoning, electrocution and poison are just three of the various ways state executions are carried out around the world. If Saga’s predictive model is correct, there are now at least four more (presumably harrowing) deaths to come, by firing squad, hanging, gas chamber and decapitation. Looks like Henrik’s dealer could end up being very busy.

Life in the village

Far from the carnage, Christoffer continued to settle in at the rural, but suspiciously serene, gated community, bonding over rifle shooting with would-be father figure Frank and playing a pheromone-charged game of truth or dare with Astrid, the local manic tricksy dream girl. Things look far less fun for mum, Sofie, after her ex, Dan Brolund, the unpleasant fists-first cabby, unexpectedly confronts her in their new refuge. Hard to imagine Dan will be cool with the whole socialist/commune/hippy thing.

Playing house with Henrik and Saga

If witnessing Taariq’s suicide wasn’t enough to send Henrik into a tailspin, the fact that teen runaways Julia and Ida had trashed his flat, nicked his family heirlooms and done a bunk pushed him deeper into despair. Saga’s non-reaction to his anguish – “I’m hungry, are you still making dinner?” – did not help, although eventually she did seem to try to reach out. Reassessing her pregnancy, she offered to have the baby, but sign over all rights and duties to him. “The child becomes yours, not mine,” she says. “And we can have sex sometimes.”

What do we know?

Morgan Sonning is implicated by Taariq Shirazi’s internet search history. It was his Audi that picked up Margrethe Thormod on the day of her death. Morgan, who has no criminal record, claims he was on holiday at the time. The car was in his brother’s garage in Sweden. Analysis shows the Audi has not been hot-wired, suggesting whoever used it had a key.

During a hostage standoff at the Swedish border, Taariq kills himself rather than face imprisonment and eventual extradition to Iran.

The Thormod investigation is expanded to include the death of Leonora, murdered by her father, William, in bizarre circumstances. Leonora was recovering from a kidney transplant in the hospital where Patrik Dahlqvist, victim No 2, worked as a clown.

The neurotoxin that killed Leonora was snail-derived, but could be sourced from an aquarium or a laboratory.

The working theory linking the stoning of Margrethe Thormod, the electrocution of Patrik Dahlqvist and the poisoning of Leonora Redberg is that the killer is echoing methods used in state executions, suggesting there will be at least four more.

Thoughts and observations