The show's bosses came up with the blaze storyline ahead of Casualty's move to new studios in Cardiff, allowing the programme to leave Bristol with a bang!
A new BBC video released online goes behind-the-scenes at the filming of the dramatic episode, showing how it was shot and how the team created the special effects.
Casualty continues on Saturday at 9pm on BBC One.
> Read our full spoiler for Saturday night's episode of Casualty
> Read more Casualty news