On 27 July 2019, Siobhan's father Stuart dropped her off at the ambulance station, but operational duty manager Jan Jenning reprimanded them for blocking the doors. Paramedic Iain Dean was tasked with showing her the ropes, and they both attended the scene of a warehouse fire. Initially, she showed initiative and helped him triage patients; when Ruby Spark asked her if she was okay, Iain labelled her "a natural". However, when a man with full-thickness burns to his torso was carried out of the building, Siobhan experienced a panic attack and left a voicemail for her father before running away; unbeknownst to her colleagues, she visited an off-licence and filled a water bottle with vodka. Once she returned, as the man's injuries were too severe for her to be allowed to travel in the back of the ambulance, she was forced to take the wheel.
Back at the ambulance station, after refilling her bottle with vodka, Siobhan found Stuart outside. He expressed his disappointment with her relapsing after four weeks of sobriety, and she vowed not to touch another drop. However, Iain overheard their conversation and demanded that she hand over the bottle. Upon smelling alcohol in the bottle, he admonished her for putting a patient's life at risk and immediately called the police. Stuart asserted that her alcoholism was not her fault, but Iain maintained that she could not "bring that sort of baggage" to work and urged him to consider whether or not making excuses for her behaviour was "the right kind of help".
Once she returned home, Siobhan berated Stuart for pouring all of her alcohol down the drain and grabbed the car keys when he refused to give her money. He rushed outside and tried to block her path, but she accidentally ran him over. An ambulance was called, and Iain and Ruby took them to Holby City Hospital's emergency department. Once Stuart was stabilised, Siobhan realised that she had to take responsibility for her actions and - despite Stuart's objections - handed herself into the police. (CAS: Series 33, Episode 46)