The second episode of this Emmy Award-winning French drama about the true story of Marie Lesnard, one of the most notorious women in the country’s recent history, cracked on unabated last night. The crimes for which Marie had been accused – the poisoning of 12 of her family and friends – had rocked France, but it seemed to me that the accusation had been built on serious gossiping and Chinese whispers from the townsfolk itself. This toxic gossip seemed to be a constant feature of the town, as young journalist Simone knew only too well - her mother was driven out of the town years earlier, thanks to anonymous letters insinuating all sorts. This was how they hounded Marie Besnard out as well. At the end of last week’s episode, we left Marie in jail, having (seemingly) signed a letter of confession to her her cell mate who, it was obvious, had been bribed to get such a thing from Marie from the cops.

This is all came to nothing, and the cell mate had soon confessed that she was put up to it by the rozzers (or should that be le rozziers?). Marie was not a happy bunny, and switched to full-on sour-face mode. Just when the friendship between these two women had threatened to melt the veneer of hardness constructed by Marie to ward off the gossips and the nay sayers, she realised she really couldn’t trust any one anymore.

But this episode was more about Simone. Because of her mother’s predicament (she had been hounded out of Loudun, had a complete breakdown and now resided in a mental home) she bought into the ‘Marie is innocent’ schtick because she didn’t want to see another woman go through the same thing her mother did – in those situations it’s always easier to side with the carping majority than speak up for justice.

Simone’s search for justice took her to into the arms of Marie’s defence lawyer, and they were engaged to be married. However, cracks soon started to appear in the relationship. If you remember from last week’s opener, Marie had a handsome live-in German fellow who did odd jobs about the house. It was obvious Marie was in love with Ady, but Simone questioned why he wasn’t around during the trial, giving Marie support.

For two people in love, Ady’s no-show struck Simone as odd, and she started to question this. When she asked Vidal, the defence lawyer fiancé, he laughed and said she took things too seriously and that she should be pleased that the case was going well (the case hinged on whether the prosecution could prove arsenic was administered when the victims had been alive, or post mortem… they couldn’t prove it and there were so many exhumations of bodies it almost became farcically comic). But something pissed Simone off and she realised that Vidal was just like the rest of them – he couldn’t care less about the facts.

Simone started to question the whole case very seriously, and her allegiance to Marie. She had a chat with mad Louise, who started the rumours in the first place (because she was having an affair with Marie’s husband). Lucille explained that Léon had confided another secret to her – that he had murdered his sister over an argument about an inheritance, and that Marie had helped him clean the crime up (they hung her from the rafters to make it look like suicide).

After more snooping around, she had totally revised her opinion - Simone was now pretty sure that Marie was the poisoner.

Marie, meanwhile, was getting on better with her disgraced former cell mate, and she was eventually released from jail on bail. The case had gone on for so long that the public had changed its opinion. It was the police who were looking stupid (because they were squabbling about the arsenic theories) and therefore making Marie look innocent as you like. A famous singer (Charles someone or other, Trenet I think it was) offered to pay her bail money. Marie had become something of a cause celebrité.

Of course, we, as an audience, hadn’t got a clue whether Marie was guilty or innocent. This ambiguity was very agreeable, I have to say, and there was one scene that crystalised this kind of is-she-isn’t-she type of thing - when Marie finally got bailed out, she went back to her cell to pick up her stuff and sank to her knees in prayer in front of her crucifix. That was nice, warm Marie. She then spotted a spider on the wall next to it, and promptly screwed up her face and battered it with her shoe. Nothing too extraordinary there, someone killing a spider with their shoe. But it in Marie’s context it was a very powerful little scene, which demonstrated the two sides to her.

Anyway, Marie went back to her old, neglected house in Loudun to battle the stone throwers and gossips. Except that they weren’t as full-on anymore… public opinion had swayed from guilty to innocent over the years and, for the most part, she was welcomed back with open arms.

A final court scene saw Louise buckle under the pressure and Leclerc (it is I! Leclerc!) went mental, exposing them for the small-town gossips they really were all along. Marie was free; the jury acquitted her.

Simone, meanwhile, went from her radio job to work in TV. She still believed Marie was the killer, and there was one final chance to have it out with her. Some years later Marie was doing a TV interview from her home, and Simone was involved in the production. Simone took the opportunity to have a chat with Marie… and revealed her own theory behind the deaths – she believed that both Marie and Léon had poisoned family and friends over the years to gain inheritance, but when Marie made it known that she was going to leave Ady everything in her will, Léon (who was violent and had proved this with the murder of his sister) went berserk. Marie, said Simone, had offed him. This theory struck a nerve with Marie, but she still refused to confirm or deny this.

I liked The Poisoner very much. Not as much as The Best Of Youth, BBC Four’s other, recent foreign-language Saturday-night fest, but it was an intriguing true story and very well acted. I Simone a great deal because, as far as I could tell, she was a made-up character who was written solely to embody the audience’s confusion about the Marie’s fate - was she guilty or innocent, that’s what Simone was constantly asking.

The final scene saw Simone, in 1980, get called to Loudun. Marie had died during the night and she had left something for Simone. When she got to the house, Marie’s housekeeper said that she had been sure Simone would come and that she insisted that she got the envelope after her death.

Simone curiously opened the envelope. There was nothing in there. To her dying day Marie wasn’t willing to give Simone a thing. Simone smiled.