WARNING: Spoilers ahead
Alfie (Shane Richie) had planned a small insurance scam, hoping a lit cigarette would cause enough smoke damage that he could claim on the contents insurance.
Instead, much to the horror of Albert Square residents, there was a huge explosion after the fire ignited a bag of hair products that had been left in the hall.
READ: HOW WILL JACQUELINE JOSSA'S PREGNANCY AFFECT EASTENDERS' LAUREN BRANNING?
His beloved Kat (Jessie Wallace) was left trapped upstairs - and, despite Alfie's heroic attempts to save her, it seems as if his outspoken wife has a long battle ahead of her as she comes to terms with her life-changing injuries.
SEE: EASTENDERS FINALLY UNVEILS CRUCIAL LUCY BEALE EVIDENCE
Tonight's episode of the BBC1 soap will see a guilty Alfie attempt to tell Kat the truth about how the fire started.
But, as he stands over his wife's hospital bed, an emotional and horribly burned Kat breaks down and thanks her husband for saving her life.
SEE: EASTENDERS REVEAL 'FIRST PICTURE OF LUCY BEALE'S KILLER'
Unable to tell her the truth, Alfie is forced to back away from his shocking confession - but, with Mick Carter (Danny Dyer) aware of the truth, it remains to be seen how long Alfie will be able to keep his secret...
Speaking on This Morning on Wednesday, Shane told co-hosts Phillip Schofield and Holly Willoughby that Kat's injuries as a result of the fire will be 'life-changing'.
He said: "For Jessie as an actress, being able to play the storyline we have got coming up after this event is brilliant.'
He added: "It will be such a departure from how we know Kat now - the tart with the heart and the heavy make-up. She will become the complete opposite to that. It is heartbreaking."
EastEnders will air on Thursday at 7:30pm on BBC1.