"End of the Line - Part One" is the 401st episode of Casualty and the 1st episode of the 18th series. This episodes sees the arrival of Tess Bateman portrayed by Suzanne Packer, who departed the show almost 12 years later towards the end of series 29.
Fin, who is carrying a diamond engagement ring, is travelling on a packed train with Comfort. Anna is also on the train, returning to Holby, but avoids the couple as she sits and takes a call from Merlin. He is still shocked she is pregnant but she makes it clear she is not keeping the baby.
While Fin and Comfort share a passionate embrace in a toilet cubicle, the carriage is de-railed to the thunderous sound of screeching breaks and breaking glass. Fin prises open the door to find hundreds of passengers in a blind panic. Initially phased by her fall, Comfort quickly gauges the seriousness of the accident and leaps into action. In the chaos which ensues, a multitude of casualties are tended to by the arriving team who are shocked by the catastrophe.
As news of the crash reaches the emergency department, new emergency nurse practitioner Tess Bateman takes control of clearing space to prepare for the inevitable rush. Simon is called in to help. But, despite being cleared of professional misconduct. He is not met with a warm welcome.
Fire chief Mike Bateman and Josh take care of the situation as ambulance and buses arrive at the embankment. Medical staff are working at such a stretch that they fail to notice that staff nurse Anna is trapped. They are horrified when they realise the gravity of Anna’s situation.
Department staff also fight to save lives and are forced to ignore those who do not have a good chance of survival. At the crash site, Nikki befriends a young boy, Paul, who is searching for his parents. And Comfort clambers through the rubble into a carriage of school children with their young teacher. Everyone works with urgency to evacuate the carriage which is under the weight of a collapsing tunnel when a sudden explosion signals disaster.