Coronation Street's Stephen eyes new scheme as he uncovers Carla's history

The killer has been helping niece Sarah Barlow (Tina O'Brien) with her new business, and is using his position at Underworld factory to enable her and Michael Bailey (Ryan Russell) to create their designs. After working hours, Sarah hired staff member Beth Sutherland (Lisa George) for overtime, while Stephen covertly let them into the building so she could sew for them.

As Beth took advantage of their situation to wangle a free takeaway, Sarah was distracted when husband Adam (Sam Robertson) made several attempts to get her attention, before he revealed that he wanted them to discuss having a baby.

Sarah was hesitant, but Adam reminded her that they had previously agreed to try for a baby, until his ex Lydia (Rebecca Ryan) derailed their plans. They were interrupted by Stephen, who needed Sarah's approval on some designs, which left Adam feeling sidelined once more.

Later, Sarah confided in Stephen that she wasn't so sure she wanted to get pregnant again after all, though she was conscious of the fact that Adam didn't have any children of his own. She went on to explain to her uncle that after son Harry was born, she had psychosis - and she was worried that the illness might return.

Stephen was shocked, but things took a turn when Sarah added that it wasn't something she talked about, and even she and Carla, who had also had psychosis, didn't discuss it with each other.

Suddenly, Stephen's interest picked up as he expressed his surprise at this news. Sarah told him that Carla's condition had led her to step back from work - and viewers could practically see the cogs turning in Stephen's mind as he mused over how Carla's past trauma could benefit him.

Coronation Street has already revealed that Stephen will begin drugging Carla next week. But while we wait to find out whether she escapes his scheme, you may be wondering how Sarah and Carla's mental health stories unfolded.

What happened to Sarah and Carla in Coronation Street?

Having dated Callum Logan (Sean Ward), the ex-boyfriend of her sister-in-law Kylie Platt (Paula Lane), Sarah eventually realised just how evil he was. After she tried to expose his crimes, Callum attempted to rape Sarah - but Kylie arrived and hit him with a wrench, killing him.

Kylie and her husband, Sarah's brother David Platt (Jack P Shepherd), then buried his body; but the traumatic event deeply affected Sarah. She later learned she was pregnant with Callum's baby, and went on to give birth to Harry.

Sarah then began to believe that Harry could sense Callum's presence. Her paranoia led her to think that Callum was still alive, and her loved ones feared for her mental health.

Daughter Bethany (Lucy Fallon) was terrified when Sarah barricaded herself inside the house, and eventually she was sectioned in a psychiatric unit, where she was diagnosed with postpartum psychosis.

Sarah made a gradual recovery, and the truth about Callum's murder continued to be covered up even after his body was found underneath the floor of the Platts' house.

A few years later, Carla was left distraught and blamed herself when the factory roof collapsed, causing the death of Rana Habeeb (Bhavna Limbachia). Unbeknownst to Carla and everyone else, Gary Windass (Mikey North) had secretly tampered with the roof in order to gain the job on the repair.

But Carla, who had hoped to rekindle her relationship with Peter Barlow (Chris Gascoyne), became ill as she struggled over everything that had happened. Peter desperately tried to reach out to the woman he loved, but Carla was arrested for manslaughter and the locals turned against her for not noticing that the roof was damaged.

Upon her release from custody, Carla was hounded by anonymous messages, written by someone pretending to be Rana. This turned out to be Rana's friend Alya Nazir (Sair Khan). However, Carla felt everyone was plotting against her, and began hearing voices. When Carla ran away, barefoot, Peter launched a search mission and it was discovered that she has been living in a hotel room.

Taken to hospital, Carla was discharged on the promise of further assessment; so she and Peter moved in with Roy Cropper (David Neilson). But Carla flooded the flat and stole everyone's phones, before believing she could see late friend Hayley (Julie Hesmondhalgh) as well as Rana. When Peter saved Carla from jumping from a fire escape, she was sectioned and sent to a mental health facility.

Carla also steadily recovered, but Stephen will ruthlessly use her experience against her. Will Carla be OK?

Anyone identifying with Sarah and Carla's experiences can find help and support for psychosis and other mental health issues via Mind.

Read more:

• Coronation Street's Todd Boyce addresses Stephen's plan to drug Carla
• 7 Coronation Street spoilers: Stephen drugs Carla and causes a crash

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