A petrol canister is knocked over, before Moira is seen with a shotgun looking angry, and she shoots out a light above her in the barn.
However, that erratic decision could be what triggers the blaze that soon engulfs it.
Newcomer John Sugden is seen telling a fellow villager: "Call the fire brigade and ambulance, tell them someone's trapped."
Cain Dingle is then seen arriving and calling Moira's name, she shouts for help - but it's not clear if she is the only one at risk before he races into the blazing barn as beams fall and flames flare up around him and Will Taylor.
Meanwhile, the gripping trailer also features more of Belle Dingle's harrowing ordeal at the hands of twisted husband Tom King.
Emmerdale's Moira Dingle suffers shock collapse after Cain calls her out for drinking
Belle is heard saying: "I love you so much, and that love is never going to go away."
Later, as she sobs, Tom is heard saying: "You look so beautiful when you cry!"
At one point in the trailer, Tom is seen falling to the ground, but in another, Belle is pinned down with a hand over her mouth.
Darkest soap storylines
Over the years the likes of EastEnders, Emmerdale and Coronation Street have all tried to try outdo each other with their outlandish plots in a bid to keep us tuning in each week. But here are some of the darkest that had fans in shock...
EastEnders: Tony grooming Whitney (2008-2009) - Tony King first appeared in Albert Square in 2008 as the boyfriend of Bianca, played by Patsy Palmer. But it was quickly revealed he was a paedophile who had been grooming vulnerable Whitney, Bianca’s adopted stepdaughter from a previous relationship, since she was 12. The shocking storyline attracted more than 200 complaints within a week of it beginning. Whitney waited until her 16th birthday to reveal the truth to a horrified Bianca, who called the police.
Emmerdale: Holly's drug addiction and shock death (2010-2016) - In 2010, Holly Barton (played by Sophie Powles) became Emmerdale's first teenage drug addict. The shocking storyline saw her taking cocaine on a night out before developing a deadly heroin habit. Parents John and Moira desperately tried to help get their daughter clean but when Holly returned in 2016, following a four-year absence, she quickly relapsed. Fans were left stunned and heartbroken when distraught Moira found Holly dead in her bed from a heroin overdose.
Hollyoaks: Luke's rape (2000) - Actor Gary Lucy was just 17 when he took on this groundbreaking storyline, which saw his character Luke Morgan become soap’s first male rape victim. Luke had endured a long-running bullying campaign by football rival Mark Gibbs - who raped him after Luke stood up to him. Luke was left suicidal following the brutal attack, before opening up to his brother Adam. Gibbs was sentenced to eight years in prison. Gary won the Best Actor gong at the British Soap Awards in 2000 for his performance.
Coronation Street: Evil Richard Hillman (2001-2003) - Just a mere mention of ‘Richard Hillman’ is enough to send a shiver down the spines of soap fans. He is often ranked one of the most evil soap villains and it’s not hard to see why. The smooth-talking financial adviser bashed his ex-wife Patricia over the head with a shovel. In a bid to keep his mother-in-law Audrey quiet, he set fire to her house. And when Maxine caught him trying to murder Emily Bishop, he took a crowbar to her head. He made his exit from the cobbles in 2003 when he drove Gail Platt, played by Helen Worth, and her family into the canal. They survived, but he didn’t.
Emmerdale viewers will have to wait and see if Belle is able to escape Tom once and for all.
It features the climax of Paul Foreman's devastating MND storyline, Toyah Battersby and Nick Tilsley's affair on the verge of being exposed and Dee-Dee Bailey trying to bring twisted ex-fiance Joel Deering to justice.