A Suspicious Discovery

The series opens with a sleeping woman on a bed; a man approaches her and caresses her face. They kiss and make love. They are Mr. and Mrs. Foster, who are happily married. Gemma is a doctor, and Simon is a property developer. When dressing up to go to work like every other day, Emma sees a lipstick slip out of Simon's pocket, but he explains it was just a chapstick for his dry lips. Emma choose not to dwell on it but notices that it's quite girly. Emma goes downstairs and says hi to their son, Tom. She can't find her scarf, so Simon gives her his. She kisses her husband goodbye and leaves for the hospital. However, at the hospital, Emma removes her coat and finds a strand of long blond hair on Simon's scarf. The day goes by, and Emma is distracted by multiple patient visits. Later, she comes back to examine the hair more closely. In the afternoon, she goes to pick up her son from school, where she is greeted by Becky, Simon's assistant. She can't help but notice the woman's long blond hair. At home, while Emma helps Tom with his homework, Simon arrives. She hands him the scarf, waiting for his reaction, but nothing weird. She then asks Simon about his business trip and how he spent his weekend there, jokingly mentioning casinos and beautiful women. Just then, their guests arrive; that evening they host a dinner with their friends, Neil and Anna Baker. Neil and Anna have just returned from a trip to a resort near the sea and share how wonderful their experience was. Gemma seems excited and keeps looking at her husband. Simon feels the need to make it seem less appealing and tells everyone that Gemma wouldn’t enjoy this kind of trip because she doesn’t like feeling trapped. However, Gemma doesn’t want to be misrepresented, so she reveals that it’s actually Simon who’s afraid of water and wouldn’t enjoy staying near the sea. She had to save his life once when they were dating. Simon is clearly embarrassed and goes to get more wine, then changes the subject, saying that it was also the day he knew for sure she was the one and proposed to her. At that moment, Anna rubs Simon’s hand, and she’s blond too, making Gemma feel uneasy again. Later in the kitchen, they talk, and Gemma tells Anna about the blond hair she found on Simon’s scarf. Anna jokes for a moment that it was hers and that she slept with Simon, but Gemma doesn’t find it funny at all. However, Anna tells her that she should trust him because without trust, she will just make herself miserable, being paranoid, suspecting everything, and so on. However, Gemma still finds it difficult to fully enjoy the night. She sees Simon's phone charging on the kitchen counter and struggles with the idea of looking through it. After the guests leave, Gemma kisses her husband and stays in the kitchen to make some tea. She again looks at the phone and finally picks it up. The next day at work, she talks about her suspicions with her colleague, Ros. They go through a list of suspects, including Becky and Anna. But Ros feels like Gemma has had too much coffee and might be overthinking things. Gemma can't focus at work and sends her patient home. She keeps wondering What Simon does in those two and a half hours every day after work before coming home. She then leaves the hospital, On the way to her car, she meets Carly, one of her patients, who asks for a prescription for strong sleeping pills because she can't sleep. But Gemma thinks it isn't safe and advises her to discuss this at another appointment. After that Gemma goes to Simon's work and watches him leaving work from afar. She calls Anna to pick up Tom for her, saying she is busy at work. Then, Gemma follows Simon's car. Simon pulls up in front of a storefront, parks, and goes in, while Gemma is stuck in her car when an old man stops her to talk.

Uncovering the Truth

He's Jack, an old doctor whom she forced to retire due to his alcoholism. He wants to change her mind and mentions he saved someone's life last night. Soon after, Simon leaves the store with a flower bouquet, and drives away. Gemma follows him. However, the location he's heading to is the nursing home of his mother, Helen. Gemma enters as well and she decides to confront Simon right outside Helen's room after asking her for a moment. Gemma asks what he does every day in the 2-hour gap between work and home, and he says he comes here to see his mom every day. Gemma feels relieved and comes inside to continue talking with her mother-in-law. However, the feeling doesn't last long after she checks the sign-in register at the front and doesn't see her husband's name on it for the previous days. She then drives to Simon's office, looks through his papers and schedule, and notices that he is marked as unavailable in the early evening quite often. She sees a work bag and looks into it. At that moment, Becky enters the room and says it's actually her bag. Gemma lies, saying she was just looking for Simon's schedule to plan a surprise party, and Becky tells her she will send Gemma an email privately. At night, the family is heading to a new restaurant named Ciao, which Gemma reveals later on their way is owned by one of Gemma's patients, Susie Parks, and her husband, Chris. They invited Gemma to come on their opening day. Simon acts weird as soon as he hears the name of the Parks. They arrive at the restaurant, and the Parks warmly greet them; Ros is also there. Chris introduces everyone to his son and daughter, Edward, and Kate, who is serving at the restaurant. They are all blond, and it reminds her of the hair strand she found. She decides to invite them to Simon's birthday party, then excuses herself to go out to get some air. Outside, she sees Carly, and Carly gives her some cigarettes. Here, Gemma tells carly about her suspicion of her husband cheating on her, and Carly tells her she needs to be sure about that. The next day, Carly comes to the appointment with Gemma at the hospital, and they make a deal: Gemma agrees to give Carly the pills in return for carly following Simon. Carly follows Simon after he leaves work, he goes to some place, and parks. Carly updates Gemma on the location. After a while, Carly finally sees the guy kiss a woman but can't clearly see her face. She then texts Gemma. Even though gemma already suspected him, when it's confirmed, she's still shocked. Gemma asks Carly to get a photo, but all she can get is a picture of the woman's car plate.

Confrontation and Revelations

Carly tells her that she can find out who the woman is, and later she comes to meet Gemma at her house. Carly checked the car plate, and the car belongs to Susie Park.

Gemma gives Carly the prescription for the sleeping pills, asks if her boyfriend wakes her up every night, and she says he did abuse her, even leaving a bruise on her arm the other night. And Gemma decides to take away the prescription and goes to meet Carly's boyfriend instead. She brings Tom with her and asks him to stay in the car as they are also heading to her cheating husband's birthday party. Gemma gets her black bag from the trunk before walking to Carly's house. She rings the doorbell, gets in, goes straight to the point, and tells the abusive boyfriend about Carly's bruise. she threatens him that if he doesn't stay away from Carly, she will send his new employer his medical record, including his drug problem and how he abuses his girlfriend. He calls her the b word and attempts to attack her, but she twists his arm and puts a lit cigarette near it, tells him to never disrespects women again. She then waits outside and makes sure he leaves Carly's house. Carly then tells Gemma that she noticed Simon keeps coming back and forth to his trunk, so maybe she should check it out for evidence of his infidelity. Gemma then goes to the birthday party with Tom, trying to act normal despite the turmoil within. Along the way, she removes he r earring and asks Simon for his car keys, claiming she lost her earring in his car. The Parks arrive and join the party while Gemma searches Simon's car, initially finding nothing. Then she looks under the spare tire and find a hidden backpack containing a wallet with a bank card, some cash, and condoms, alongside a phone. The phone's background image is of Simon holding a young blond woman who is not Susie but Kate, her daughter. Gemma gasps in shock, her disgust growing as she browses through photos of Simon with Kate, hanging out with Becky, Anna, and Neil. Even Ros, her colleague, has texted Simon, says she think Gemma is following him. Overwhelmed and struggling to breathe, Gemma tries to compose herself and get a pair of scissors from her bag, tucking them into her pocket.

The Final Unraveling

Back at the party, Gemma can't look at people the same way. Simon accidentally burns himself, and while helping him, Gemma takes his wedding ring and puts it in her pocket. Holding the scissors tightly, she thinks about hurting Simon but he walks away to give a speech. Simon thanks Tom and Gemma, calling them the best things in his life. Gemma forces herself to not throw up and goes up to kiss him, making Kate, who is watching, angry. As the gathering dissolves to dine, Gemma is left alone with her thoughts spiraling into the deep hole of a woman scorned.