The Serpent on BBC has provided some gripping Sunday night viewing since it began earlier this month.
It seems each episode has left fans on the edge of their seats, but it was episode four that they found particularly anxiety-inducing. Warning: episode four spoilers ahead!
After realising that Charles Sobhraj and Marie-Andrée Leclerc, under the guise of Alain and Monique, were responsible for poisoning Dominique and killing countless others, Nadine and Remi decide to help Angela and Herman Knippenberg in bringing down the criminals.
WATCH: Official trailer for terrifying drama The Serpent on BBC
But it was Nadine's risky undercover work taking photographs of the suspects that left fans feeling anxious while watching the tense episode. One person tweeted: "God these Nadine scenes are tense. I just got over last week with Dominique. Heart can't take it #TheSerpent." Another fan wrote: "Finding that the wellbeing of Nadine and her safety is my only concern #TheSerpent."
Others was feeling particularly concerned for the character. One tweeted: "I don't think I've ever had such anxiety for someone as I do for Nadine looking through their apartment #TheSerpent," while another added: "It takes me seven days to adjust, all last week I was worried for #nadine This week I'm worried yet again for her whereabouts! #TheSerpent #rivetingwatch."
Episode four saw Nadine take on a risky undercover task
Elsewhere in the episode, Marie-Andrée and Charles came to blows when she expressed she had had enough of his criminal ways, however it didn't take long for her to become wrapped up in Charles' behaviours again. Viewers also saw what happened on their Christmas trip to Hong Kong – which turned out to be to Kathmandu after all.
Episode four also focused more on his other accomplice Ajay, and how he is becoming more despairing of Charles' actions, particularly after he meets a love-interest.
The serial killer, who was reprimanded in 1976, took Ajay on a shocking killing expedition as he murdered two backpackers in a brutal attack – and from the look on Ajay's face, he feels under the control of Charles' heinous behaviour.
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