The soap launches a dramatic mystery storyline later this week as one of Cain's enemies brutally attacks him before leaving him for dead.
Emmerdale bosses have named John and Moira Barton (James Thornton and Natalie J Robb), Jai Sharma (Chris Bisson), Charity Tate (Emma Atkins), Amy Wyatt (Chelsea Halfpenny) and Zak Dingle (Steve Halliwell) as the main six suspects in the case, but viewers will not discover who was responsible until the New Year.
Hordley told This Morning today that he and his fellow cast members were also in the dark for much of the filming process.
"You don't find out until January - it's absolutely brilliant," he explained. "I know [who it is] now - we only found out just recently because we've just shot the episode. It was a very closely-guarded secret."
He continued: "We don't want it to get out. Mum's the word! But it's great - it's a fantastic storyline. I'm so thrilled to be part of it. I think the rating figures last week spoke [for that] - not that I'm bragging about it, but we beat Corrie and we beat EastEnders last week."
Emmerdale airs Cain's 'Judgement Day' in a double bill on Thursday evening, which sees the village villain insult all of the customers in The Woolpack one-by-one in the moments leading up to his attack.
Hordley added: "It was a brilliant scene. It's quite Tarantino-esque in the way that it's written. We've got a fantastic writer who's written the episode - you laugh at some points and you know that you shouldn't be laughing. It's fantastic. It's a very strong episode and I'm really proud of it."
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