Emmerdale spoilers follow.
Emmerdale's Mackenzie Boyd leaves his friend Aaron Dingle crushed next week – suddenly announcing that he can't be his best man.
Mackenzie makes his sad decision as he faces a furious backlash in the village over a contaminated water scandal.
This week's episodes feature a dangerous leak with the slurry tank at Butler's Farm.
Mackenzie is blamed for the incident and there are far-reaching consequences when the slurry contaminates the village's main water supply, causing Victoria Sugden's young son Harry to fall ill.
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Next week, Harry is still on a drip at the hospital after drinking the water and Victoria is frantic with worry.
Poor Mack finds himself public enemy number one in the local community, as everyone mistakenly blames him for being reckless.
"Mack is facing anger all round as everyone worries about Harry's future," our Emmerdale source explains.
"There are problems closer to home too, as Mack's sister Moira is awaiting a hefty bill for the clean-up of the slurry.
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"The financial implications are so major that Moira may have to give up the farm altogether after 16 years at Butler's."
In a potential clue to the real culprit, deceptive John Sugden becomes overwhelmed with his own guilt over his nephew Harry's condition. He can't help snapping at husband-to-be Aaron when the stress becomes too much.
Mack then breaks down in John's arms, with all previous animosity between the two men put to one side for now. Seeing just how serious this situation is, John is mortified.
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As stressed-out Mack continues to be ostracised by the other villagers, he decides to back out of being Aaron's best man.
With the wedding just one week away, Mack doesn't think it'd be the right time to paint on a smile and play a key role in the celebrations.
"Aaron is gutted by Mack's decision and wants to stand by his friend," our insider adds.
"John is concerned by Aaron's reaction, wanting everything to be perfect for him. He comes up with a plan to get Mack back in the fold, but will it work?"
Emmerdale airs these scenes on Monday 19 May on ITV1 and ITVX.
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Emmerdale airs on weeknights at 7.30pm on ITV1, and streams on ITVX.
Read more Emmerdale spoilers on our dedicated homepage
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