Lia’s character, Alice Warner, was interrupted by her son Simon (played by Finn Bennett) as she took a shower in the third episode of the series.
Creepy Simon proceeded to detail a sexual encounter he had with a girl at his school while his mother asked him to leave.
The schoolboy ripped the towel from Alice’s naked body after ignoring her pleas.
Lia, 53, has commented on the scene that left many fans of the Channel 4 show reeling.
The actress revealed in a conversation with Radio Times: “It was a very difficult scene to do but it’s so intelligently done and I trusted everyone around me so much.”
She continued: “I just thought it was a really great scene because it’s so alarming. It’s one of the things that made me want to do it.
“I didn’t shy away from it at all, quite the opposite.”
Fans of the show were disgusted by the creepy interaction and made their views known on Twitter.
One wrote: “The mother and son in Kiri are seriously sending me some STRANGE vibes.”
“What’s wrong with this boy? Staring at his mum in the shower and all! #Kiri,” questioned another.
“Simon walking in on his mum in the shower and pulling her towel away. That’s some worrying behaviour. #Kiri,” a third stated.
Finn and Lia’s relationship is far cry from the unsettling one they portray on screen, as Lia divulged they unwound together after they finished filming the intense scene.
She said: “Finn and I had a drink together in the hotel we were all staying in afterwards. We get on like a house on fire.”
Simon’s odd behaviour has lead to questions about his involvement in Kiri’s murder.
The teen’s actions, coupled with lying about his whereabouts at the time of the killing, have placed him as a prime suspect.
However, viewers will have to wait until the final episode next week to see who the guilty party really is.
Kiri continues Wednesday at 9pm on Channel 4.
