Kyle Braxton, who is serving a thirteen year prison sentence, is suddenly moved to the Protection Unit because the Braxton family's enemy Trevor "Gunno" Gunson has returned to the prison. Kyle receives a visit from his brother Heath Braxton and his wife Bianca Scott. They explain how Gunno recently kidnapped Bianca and held her hostage. Prison inmate Bandit informs Gunno that Heath and Bianca are visiting Kyle, and Gunno instigates a riot in order to send the prison into lockdown. Gunno and Bandit break into the security command centre, while the prisoners from the protection unit are attacked. Kyle drags Prison Guard Mayhew out of harm's way after he is injured. As Heath and Bianca are being escorted towards an exit, Gunno takes over the PA system and tells the inmates to bring them and Kyle to him. Realising they cannot leave, Heath and Bianca hide in a ceiling crawlspace.
In Summer Bay, Heath's daughter Darcy watches a news broadcast about the riot, but Irene Roberts tells her that it is occurring at a different prison. Irene calls Nate Cooper and Martin "Ash" Ashford, who agrees to go to the prison and find Heath and Bianca. Mayhew wakes up and Kyle asks him for his keys, so he can get them out. Prisoner Frank uses Mayhew's radio to tell Gunno where Kyle is. Gunno opens all the doors, allowing the prisoners from general population to enter the protection unit. Kyle and Mayhew escape to the laundry room. Meanwhile, Ash and Nate go to the back of the prison, where Ash gets inside through a secret entrance that Gunno used for drug trafficking. Heath and Bianca are forced out of the crawlspace when it fills with smoke and Ash finds them. He guides them to the exit, but Heath realises he cannot leave Kyle behind and tells Ash to get Bianca out.
Bianca begs Ash to go back for Heath and she collapses in Nate's arms, before telling him she is pregnant. Gunno sees Kyle on a security camera and he goes to the armoury to get a gun. Heath changes into a prison uniform to blend in, and Ash catches up with him. Gunno shoots Kyle and leaves him for dead. As Irene watches the news, Darcy realises that she lied to her. Irene assures her that Heath will protect Bianca. Heath calls Bianca to say goodbye in case he does not make it out. Isla Schultz, the woman Kyle went to prison for, recognises Bianca and introduces herself. Isla wants to let Kyle know that she still loves him. Ash and Heath find Kyle and stem his bleeding, before Heath helps him to the exit. He encourages Kyle not to give up when Kyle wonders what he has to live for, as Isla has not visited in months. Heath gets Kyle outside, where he is handcuffed and Kyle is put into an ambulance.
Gunno puts on a guard's uniform, but Ash notices him and gives chase. Gunno tries to shoot him, but misses. Mayhew alerts Ash to Gunno's hiding place in the laundry room. Gunno tries to shoot Ash again, but the gun fails to fire and they fight. Ash pushes Gunno backwards and impales him on a clothes hook, killing him. Mayhew tells Ash that he will take the blame for Gunno's death. Heath and Bianca call Darcy to let her know that they are okay. Kyle and Isla reunite and she admits that she stayed away because she felt guilty. Kyle tells her that he does not blame her, but he needs to know if they have a future and Isla kisses him. Mayhew tells the waiting journalist that he is responsible for the death of an inmate, and that he wants to recommend that Kyle has his sentence reduced for saving his life. Later that night, Bianca finally tells Heath she is pregnant.