In Cardiff, paediatric urology surgeon Selena Curkovic is determined to operate on Barney — an eight-year-old who has waited five years for surgery that could transform his life. At the University Hospital of Wales, spinal consultant Stuart James has such a full operating list that he's had to open a second theatre. With theatre time rapidly running out, Stuart must decide which of two patients he must prioritise and which he must cancel. Meanwhile, thoracic surgeon Tom Combellack at University Hospital Llandough is operating on Jan, who has a suspicious growth on her lung. But it's so close to her heart that the usual procedure to check if it's cancerous is too dangerous, and Tom must operate straight away.