Sadie was Harry's girlfriend when Harry went to boarding school. After Harry's failed marriage to Ste Hay and his break up with James Nightingale in October 2018, he went to stay with Sadie. They had sex in November which resulted in her becoming pregnant and deciding to keep the child. Harry was unaware of this when he returned to village in January.
Sadie started texting Harry, asking for his help in April 2019. When she arrived in the village, she told Harry she was pregnant and that her parents had kicked her out of the house for being pregnant out of wedlock. On the night of the hit-and-run on Grace Black, Harry was paying her money to permanently stay out his life as he wanted nothing to do with the baby.
Sadie demanded more money from Harry and Harry mets up with her, explaining that he felt that they needed to move on with their lives but Sadie wanted Harry to step up and showed up the next day with her belongings. Harry took her to 14 Weirside View. When Harry's boyfriend, James Nightingale, returned home suddenly, and Harry hid her. A few minutes later, Sadie introduced herself to Harry and exposed the secret that Harry had been keeping from James. She also tells James that Harry will be a father to her child, whether he likes it or not. The next day, James delivered an ultimatum to Harry - him or the baby. Harry chose James and informed a furious Sadie of his decision. When Harry asked if Sadie could get moved into a council house, she questions why she should have to, since her baby has two parents. Harry then agreed to look after her and the baby, even if it meant losing James.
Harry asked Sadie to go to the police to give him an alibi, but as Sadie was about to leave, Liam Donovan (who caused the accident on Grace) offered her money in exchange for leaving the village without giving Harry an alibi. When Sadie later discovered that Harry lied to her about telling James about his decision, and that Harry only wanted her to get a statement, she agreed to Liam's offer. Sadie took the money as she watched the police arrest Harry, and left the village.