'EastEnders' is set to be rocked by a huge fire that tears through the Slater family's home later this year.
The loud-mouthed relatives could be left fighting for their lives after a fellow Walford resident deliberately sets their house alight in September.
A soap insider told the Daily Star newspaper: "This is one of the biggest storylines of the year and will kick-start an action-packed autumn in Albert Square. The fire isn't a big stunt, it's more about what happens in the aftermath.
"It's going to be a very moving and emotional storyline as at least one person is rushed to hospital with life-threatening injuries."
Kat and Alfie Moon (Jessie Wallace and Shane Richie), their son Tommy, newborn twins Bert and Ernie, Stacey Branning (Lacey Turner), her mother Jean Slater (Gillian Wright) and Big Mo (Laila Morse) will be among the characters trapped inside when the deadly fire sweeps through their home.
The source explained: "It's going to be heartbreaking as the scenes play out. There was lots of screaming and crying when we filmed the fire episodes and when they are finally broadcast we're certain there won't be a dry eye anywhere in the country."
However, viewers are set to be stunned when they find out which resident is responsible for lighting the match.
The insider added: "Everyone will be shocked when they discover who it is.
"The arsonist will have to live with the consequences of his or her actions for the rest of their life."