'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 aggressively wipes 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."

J.B. Gill blames his wife's pregnancy cravings when he wants snacks.
The former JLS singer and his new wife Chloe Tangney are expecting their first child together and the 'Beat Again' hitmaker admits to blaming his spouse when he made a large order of calorific treats on their honeymoon the the Seychelles recently.
Speaking to new! magazine, J.B. joked: On our honeymoon we booked an all-inclusive package so we could order whatever we wanted.
"One day, I called them up and ordered chocolate bars for myself and blamed it on Chloe's cravings. I was like, "Bring everything up - Snickers, KitKats..."
So far, dancer Chloe is having a good pregnancy and hasn't suffered anu morning sickness.
J.B. said: "We've been really lucky. She's not had any sickness and she has been able to work."
The singer-turned-farmer recently admitted he was shaking with nerves at his wedding, which took place in May.
He said: "When I saw the first bridesmaid, I was like, 'Wow'. I was shaking and I didn't know how to stop. Then Chloe's sister Sian Louise came in and she was really emotional. I thought, 'I'm going to lose it'.
"By now, I was desperate to see Chloe. I'd missed her. Then, when I saw her coming down the aisle with her dad, I felt calmer. They weren't in meltdown, they just looked really happy and that helped me to hold I together. I know it sounds cheesy, but it was perfect."

Peaches Geldof's sisters have stepped in to help her widowed husband care for their children.
Fifi Trixbelle, 31, Pixie, 23, and Tiger Lily, 18, have vowed to help Thomas Cohen, 23, raise sons Astala, two, and Phaedra, 15 months, following the tragic death of their mother Peaches, 25, on April 7.
A source told the Daily Mirror newspaper: "It's really impressive how the sisters have taken on the role of caring for the boys. Peaches would be so proud.
"Fifi, Pixie and Tiger have been amazing with the kids and such a help to Tom. Everyone wants to make the boys part of a solid family unit. They were all up in London recently. It was good to see their smiles."
The S.C.U.M rocker, who married the blonde beauty in 2012, is too traumatised to return to their marital home in Wrotham, Kent, after he discovered his wife's body slumped over their bed from a heroin overdose three months ago.
He has since been staying at his parents Sue and Keith's home in Eltham, South East London, with Astala and Phaedra.
The insider added: "Tom's family are doing a fine job and the sisters are great. There's a lot of sitting around watching [children] TV shows like 'In the Night Garden' - things Peaches would do."
Earlier this week, an inquest into Peaches' death revealed the mother-of-two had begun taking high purity heroin again in February after two-and-a-half years using the substitute drug, methadone.
Drugs paraphernalia - including knotted tights, a capped syringe with brown residue in the main chamber and burnt spoons - were found in the home by police at the time of her death.

Harry Styles' girlfriend has threatened to call the police after she received hate mail from his fans.
Paige Reifler, 18, is tempted to seek law enforcement back-up over the bombardment of death threats from jealous One Direction supporters after she confirmed last week she is "seeing" the 20-year-old hunk again.
Taking to her Twitter account last night (26.07.14), Paige refused to ignore the internet trolls, writing: "I hope you all know that giving die threats is a crime, I could report you to the police. The hate can be also reported. I just can't stop laughing at some tweets. I can't believe it yet."
The couple sparked rumours they had rekindled their romance after they were spotted getting cosy over a few alcoholic beverages at an exclusive party at Shoreditch House in London earlier this month.
An insider said at the time: "Harry turned up specifically to meet up with Paige but they were as discreet as possible at the event. Then they both left the main party, which was on the rooftop next to the pool, and went downstairs to the more private restaurant.
"They were having drinks with her agents. But Harry ended up putting his arm around Paige and they were very flirty together. They ended up leaving on their own because there were lots of photographers outside."
However, a friend of the pair believe their relationship is unlikely to blossom into anything too serious at this stage as their respective careers will get in the way.
The source said: "Paige is completely smitten with him but realistic that their crazy lives mean it might not be able to develop into anything serious at this stage."

Dame Helen Mirren wanted to be a French actress.
The 68-year-old star has played the head of the British monarchy in 'The Queen' but she's admitted that her new film role as a restaurant boss in the South of France in 'The Hundred-Foot Journey' is the character she most relates to.
She explained to HELLO! magazine: "What I loved about ['The Hundred-Foot Journey']- I could pretend I was a French actress for the first time in my life."
Helen revealed that whilst she was a teenager living in the South East of England, she dreamt of becoming a French actress and even bought a property in Paris.
She shared: "When I was growing up in my teens , the French just seemed to be the coolest, most chic people on the planet and I desperately wanted to be French. I got myself a French boyfriend and that was the closest I could get to it.
"I did a film in France and I loved being there. I rented a little garret and it was literally one room on the top of a house on the Left Bank and it was very bohemian. I thought I would literally just go to Paris and just sit there until I became a French actress."
However, it was never to be as Helen was getting more recognition in her native England.
She reflected: "I kept getting work in England, which I had to take because I had to pay for the garret in France and then it just never worked out."

Manic Street Preachers want to make "the biggest f***ing rock record ever".
The Welsh trio have just released their 12th album, 'Futurology', which has been one of the most well-received of their career, but they are already looking ahead to the future and have set the bar high for themselves.
Bassist Nicky Wire said: "I think we all know deep in ourselves that there is only one record left to make and that's the biggest f***ing rock record ever.
"It's Zeppelin, it's the Pistols, it's [debut album] 'Generation Terrorists', but bigger.
"That's a long way off. But I think we know that's what's left; to raise the scales to an enormous level."
The 'Walk Me to the Bridge' hitmakers are very happy with their new album even though they think their intentions with the record were "ludicrous".
Nicky added to NME magazine: "It's ludicrous in its ambition. We're trying to talk about abstract art movements in a f***ing three-minute pop song, and there's so much eastern Russian stuff in there on songs like, 'Black Square' and 'Mayakovsky'.
"It's got the same ridiculous ambition as 'Generation Terrorists' but it's more cultured. It has that intent though, it's got the post-punk jaggedness of 'The Holy Bible', but it merges that with the retro-futurism we've always been obsessed with."

Kerry Washington was nervous about joining Twitter.
The 37-year-old actress joined the social networking site as she wanted to be able to interact with fans of her hit US TV series 'Scandal' but she's admitted she was reluctant at first.
Quizzed on whether she's happy she took the leap, she said: "Yes. There is a real power in social media. The world has become a global community and that's very exciting. [But] I'm a very private person so I was nervous about it.
"I didn't know how to interact in this way without feeling like I was violating a sense of having a personal life outside and separate from work."
The 'Django Unchained' actress - who has three-month-old daughter Isabelle with her husband Nnamdi Asomugha - is also a keen supporter of charities which fight for equality.
Kerry explained to Stylist magazine: "I've gravitated a lot towards women's issues because I'm a woman. Also, I believe in equality for all members of our community and that lends itself to being very active around voting, voters' rights and participating in a democracy.
"Our voices are heard in the US by showing up and voting. It's important that people know they own that privilege."

Sir Ian McKellen "lives within his means".
The 75-year-old actor - best known for playing Magneto in the 'X-Men' franchise and Gandalf in the 'Lord of the Rings' movies - insists he has always been careful with money and it wasn't until he entered his twilight years he began living comfortably with plenty of money in the bank.
He said: "Money is a factor in my life but it's not a major factor. I've never had to worry about it - I learnt very early on to pay my taxes on time and live within my means, which has served me well.
"And I haven't had to bring up a family and I don't have dependents.
"I haven't earned an awful lot of money until quite recently. At the same time, I've never had to do a job for the money so I've been very lucky."
The legendary screen star says many actors struggle financially but continue pursuing their career of choice because of passion.
He explained to Radio Times magazine: "Most actors are not rich - they are very poor indeed. What keeps them going is that they just love the job. I know actors who have had to turn down good roles because they just don't pay enough. It's hard.
"The one thing you can ask, I think, is that actors get paid a living wage."

Kanye West reportedly wants to turn Kim Kardashian into the "perfect" wife.
The 'Bound 2' star is said to advise his spouse - with who he has 13-month-old daughter North - on every aspect of her life, and has even ordered her to stop smiling for photographers when they are out together.
A source told Britain's Grazia magazine: "Kanye can be very controlling with everything in his life, that's his personality. He wants Kim to be perfect.
"In the old days, you'd always see Kim smiling when she was having her photo taken. But now, more often than not, she'll be stony-faced."
Kanye's controlling ways are said to have left the 'Keeping Up with the Kardashians' star with a crisis of confidence and she can't even bear to make small decisions alone.
The source added: "It seems even when he's not around she can't make decisions. Kim will call him to check she's buying the right brand of water.
"She can't even pick her own nail varnish without checking with him."
The brunette beauty has previously admitted to changing her clothes if her husband doesn't like her outfit.
She has said: "I'll put something on and he's say, 'No, that doesn't look good,' and I trust him."

Kate Garraway wants a baby at 47.
The 'Good Morning Britain' host has admitted she'd love to fall pregnant again with her husband Derek, with whom she has daughter Darcey, eight, and son Billy, four.
She said: "I'm 47, there's a big change in your fertility at that age. But I'd love to fall pregnant with a third baby - we both would. But life is really full and it's just pure greed on my part!"
Kate has ruled out adoption, however, explaining that her career is so busy she'd need to make more time to help the child adjust.
She explained: "If you're taking on a child that may already have issues or problems, I think I'd like to feel I had more time. I'm really lucky though and have a lovely family."
The TV journalist feels motherhood has made her more conscious of her health and diet as she wants to ensure she is around for her kids.
Kate told new! magazine: "Now I've had children I feel health is more a priority rather than obsessing over the way you look in a pair of skinny jeans. Though I would love to look good in a pair of skinny jeans!"

Kendra Wilkinson is "done" with her marriage.
The 29-year-old reality TV star was left devastated after claims her husband Hank Baskett cheated on her with a transgender model while she was pregnant with their second child and friends close to her say she has no interest in reconciliation.
A source told PEOPLE: "Hank and Kendra are on speaking terms, but she's still so mortified by the situation. [The cheating] happened before, but she's done [with the marriage]. It's more about the kids and the finances now. She's an optimistic person and wants people to know she's doing better."
Although the fallout from the affair claims is set to air on her reality TV show 'Kendra On Top', Kendra is said to be unhappy about it.
The insider said: "They're contractually obligated and are in the middle of filming. But she doesn't want people talking about it for the rest of her life. She just wants to move forward."
The couple married in 2009 and have son Hank IV, four, and daughter, Alijah, three months together.

A fast food worker "screamed" at Aretha Franklin in Canada this week.
The legendary singer came under fire when she tried to eat her to-go meal in a Johnny Rockets restaurant in Ontario on Tuesday (22.07.14), her spokesperson claimed.
In a statement Aretha slammed the employee as "very rude, unprofessional and nasty" when the 72-year-old legend stopped at the eatery following a sold-out show at the Artpark Outdoor Amphitheater.
A Johnny Rockets spokeswoman said the owner of the franchise of the popular chain is sorry for the actions of "a new and very young employee".
She added that the owner has spoken to the staff about takeout policies.
Aretha celebrated turning 72 earlier this year and revealed her birthday wish was to have her talented family members land record deals of their own.
She said: "I'm looking for a record deal for my granddaughter Victorie and my son Kecalf and Jordan, who is going to school for the arts at the end of the year, so he's on the way."