And the official Corrie website at itv.com/corrie now reveals the truth - and we finally find out what Craig knows.
The official website says that in next week's episodes Karl finds Craig (Colson Smith) in tears, believing that he is responsible for the fire. An upset Craig opens up to Karl that he threw away a lit cigarette because he saw him leaving the pub and didn't want to get caught smoking.
Karl knows that if Craig tells anyone then it will expose him as the arsonist, as he told police he was at the Bistro's Full Monty event all evening.
John Michie, who plays Karl, says: "It definitely crosses Karl's mind that he might need to silence Craig for good. When he meets him at the disused railway bridges, killing Craig is definitely on his mind."
Karl employs scare tactics to keep Craig quiet, telling him that if anyone finds out that it was his cigarette that caused the fire he could go to prison for killing Sunita and Toni the firefighter.
"He’s hoping that he can scare Craig enough so he doesn’t say anything until way after the wedding. By that time Karl will be in Spain and he has no intention of ever coming back to Weatherfield. Karl threatens to kill his mum, Beth. This is the last card he can play with Craig. The implication being "if I can kill your Mum, I can kill you..."
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