"Belief" is the 966th episode of Casualty and the fifth episode of the 30th series. It was preceded by "Cradle to the Grave" and followed by "All the Single Ladies". The episode was directed by Steve Hughes and written by Mark Catley. It focuses around the events when two sides of extremism clash, causing havoc in the ED.
At a mosque in Holby, an attacker uses spray paint to write "Muslems out" on a banner. As a local attender of the mosque, Arshad edits the graffiti to shame the attackers bad grammar. Meanwhile, another local Muslim man named Ibrahim is cleaning a clubhouse ready for a group of people who turn out to be right wing activists. During their meeting, he enters the room and drops an acid bomb of sorts on the table causing burns to leader Roy Ellisson and his wife Denise as well as many others. When Ibrahim is escaping on his motorcycle he skids and his motorcycle skids towards a bus stop where Arshad's wife and young son are waiting, killing them both.
Meanwhile at the ED, Salmar and Mairo are waiting to be seen for a cut on her arm, and Connie has to ask a man in reception to move seats when he refuses and won't communicate, but can talk to Jacob in Arabic. After Roy and Denise are admitted to the ED, Jacob looks for Mairo who has gone missing, but Salamar claims she has just gone to the toilet. During their conversation, Salamar begins to act suspicious, questioning how good the reception is in the ED as a text isn't sending to his friend. When it eventually sends, it's revealed that the man in reception is the friend, and upon receiving the text fires gunshots into the air leading to an evacuation of the ED. However, Alicia, Louise and Max are stranded with Roy in resus as it is too risky to move him. She performs a risky procedure in order to save him.
It's then revealed that Mairo has gone and changed into nurses scrubs to disguise herself while she attempts to find Roy or Denise. After Arshad is called into the ED by Robyn, he comes upon Ibrahim and confronts him about the fact he killed his wife and son. As Mairo is loose in the ED, she tricks Denise and takes her upstairs where Salmar is waiting. They encounter Big Mac on the way who mistakes them for endangered patients, but realises that he is mistaken when they hold him at gunpoint once he has led them into the boardroom, and make him record them making Denise read out a script before they kill her. During the commotion, Jacob insists that him and Connie go back inside the ED to get Alicia and the others. Along the way, they hear the voices from inside the boardroom and upon opening the door are also taken hostage.
While waiting outside the ED, the police ask Ibraham to call Salmar and stop him, and request that Rita and Lofty keep him on the phone while they send in their forces to free the hostages. When Mairo puts a gun to Denise's head, Jacob manages to retreive a gun from the table that Salmar had put down, and points the gun at her. When the police enter the room, they shoot Jacob in the arm realising he has a gun, only after noticing that he is not one of the attackers. Salmar and Mairo are arrested, and Connie takes Jacob to resus. Elsewhere, Arshad goes to pray and asks Robyn to stay with him. Back in the recovery room, Connie goes to check up on Jacob, and tells him people will look up to him, but he says that he feels more like a victim than a hero.