"Gravity" is the 896th episode of Casualty and the 29th episode of the 28th series . It was preceded by "Survivor's Guilt" and was followed by "The Lies We Tell". The events of the episode took place on 8 March 2014 as it was a direct follow up of the previous week.
Continuing from the previous episode, Big Mac tells Kenny that Iain's on his break. He keeps asking and eventually gets angry with Mac and pushes him, and he hits his head on one of the oxygen tanks and receives a nasty cut to his head, knocking him unconscious. Meanwhile at a house party, a woman from next door goes to complain that her child with cerebral palsy can't sleep. The host is also the boy's dad, but when he refuses to turn it down, she throws his speakers off the balcony. In anger, the man pushes her and she falls back into the railing which gives way and she falls onto a parked car.
Iain leaves a message for Big Mac on his phone telling him that he's heading back to the ambulance station and to look out for Kenny. However, Big Mac is unconscious and Kenny listens to the message instead. Elsewhere Dixie and Jeff arrive at the scene of the accident at the house party and take the woman back to the ED. Meanwhile Iain goes into the ambulance station in search of Big Mac and finds him sitting on the ground barely conscious. Kenny walks in and although Iain tells him that he's not sleeping with Beth, Kenny says that no one's leaving until he gets the truth. Iain explains that the phone calls to her were so they could try to help him, not because they were having an affair.
Back in the ED Natalie Fletcher arrives in the early stages of labour to Fletch's surprise. Back in the ambulance station, Kenny continues to keep Mac and Iain hostage. When Kenny asks where Iain was before he went back to the ambulance station, Mac lies and tells him that he told Iain to go to the hospital to pick up supplies. However, Beth soon arrives outside the ambulance station and inadvertently reveals that she was with Iain, not knowing they had lied to Kenny. Kenny threatened Mac with a metal pipe and told Iain it was his last chance to confess. Dixie and Jeff arrived in the ambulance and called for police backup when Beth explains the situation to them.
With armed police and a helicopter outside the station, one of the police officers uses an announcement system to tell Kenny to answer his phone so the situation can be resolved peacefully. He still continues to think Iain and Beth are having an affair. Back in the ED the woman who fell of the balcony is recovering and her ex boyfriend who was also at the party reveals that their son is still at home and realises he needs help. Back at the ambulance station, Iain reveals to Kenny that he too was affected by what happened in Afghanistan as he was responsible for killing their friends. When Kenny asks how, Iain reveals that he saw what the man with the bomb was going to do and he should have thrown himself on him before he had chance to get to the rest of the unit. Kenny then tells Iain that it wasn't his fault and that it was the man with the bomb who tricked him and gained their trust. Kenny then tells Iain that he believes that he isn't having an affair with Beth, and Iain is able to take the pipe off of him.
In the ED the father of the boy informs Charlie that his child has cerebral palsy and is at home alone and needs help. Jeff and Dixie go to help and are able to reach him in time. Natalie gives birth to the baby and asks Fletch to go back home and live with them again. In the ambulance station Iain opens the doors and Kenny is apprehended outside. Big Mac is safely taken into the ED and receives treatment for his head injury. Beth goes to see Iain in the ED and tells him that the police won't let her see Kenny. They say goodbye to each other and Beth tells Iain to tell Mac they're sorry. Dixie tells Iain that she will need to take a statement from him tomorrow about the events and also that the police will require a statement.