Spoiler alert! If you haven’t watched the final installment of Discovery’s three-part gold-rush miniseries Klondike, stop reading  now. Star Richard Madden chatted about the ending — from its surprising potty humor to the nightmares it gave him.

At first, it seemed as though Bill Haskell (Madden) and his mining pal Joe Meeker (Tim Blake Nelson) would make it out of the Yukon alive — and rich. Meeker had hidden some of their sought-after gold at the bottom of their makeshift toilet. Madden’s reaction to that particular twist? “I thought exactly what the line at the end of the scene is, ‘Well, who’s gonna go get it?’ ” he recalls, laughing. “I thought, ‘Oh god, is there gonna be a scene with me knee-deep in all this s— with gold in my hand? I don’t want to be doing that.’ This is three months into the shoot. I’ve been battered and bruised. I would say at least 50 percent of the shoot, I would get back to my apartment and wake up the next day on the sofa in the clothes that I arrived home in because I was so physically exhausted. I’m like, ‘Are we really gonna do that?’ And luckily, we didn’t.”

He confirms the he and Nelson were looking down into the toilet at what the camera shows viewers: “These amazing prop poos are so unbelievably realistic,” he says. “I couldn’t get over it. They were disgusting. The only thing it was lacking was the smell, and you know when you see something so believable you actually start to smell it, so you start to hold your breath? That’s what we were looking at.”

As Haskell and Meeker made their exodus across a frozen lake, Meeker, who was carrying the gold, fell through the ice and died. “We were actually on that frozen lake, and you hear these massive gigantic booms, like there’s a nightclub underneath you, and that’s whole sheets of ice dropping,” Madden says. “There was one day where we were going for a take, and we heard this massive boom, and the shelf that we were on dropped, maybe only six inches, but when you’re in the middle of a frozen lake, that is huge. I turned around to see all the crew running back to shore. So I start to run as well, and then eventually everybody goes, ‘Be cool, be cool, be cool,’ and everyone slows down and turns around and pretends that they’re not terrified that they’re not gonna fall through the ice.”

In his head, he knew they were safe — the ice had been tested before shooting began and was “ridiculously thick,” Madden says —  but it didn’t stop him from having nightmares after filming the scene. “Because there is just no way to survive it, especially when you’ve got a current underneath like that lake that we were on did. Just like in the scene, you’re sucked under, and the ice that you’ve fallen through comes back up and forms a ceiling so you can’t get back up the hole you’ve fallen through. It’s one of the most horrible ways to die, I think. It literally gave me nightmares. It was toward the end, and I’d become very close to Tim Blake Nelson, and the characters had developed in such a way that I found it a really disturbing, terrifying thing to shoot.”

In real-life, Haskell did make it out and wrote a book, Two Years in the Klondike and Alaskan Gold Fields 1896-1898, and as in the miniseries, no one is sure how he eventually died. “That’s what’s amazing. Charlotte Gray, who wrote the book [Gold Diggers: Striking it Rich in the Klondike] that Klondike is based on, and I had great conversations because she searched and searched and tried to find out what happened, and there is nothing. No one actually knows what happened to him after he wrote the book. There’s no written evidence, no pictures. It’s a strange, beautiful mystery. It leaves the audience the same way I’ve always felt, which is [thinking] what do you take from this? What does it do to you as a human being when you go through all of that? The gold and the wealth that you have at the end isn’t what you gain from this experience, it’s an understanding of human beings,” Madden says. “What stands out in the end of all the books, reports, and diaries that I read is human kindness — that’s what pulls everyone through it. Even though you expect people to be so cutthroat and animal in these situations when you’re fighting over the smallest scraps of food, or mud, or gold, human kindness actually prevails. That’s something that I loved about the end, and then it doesn’t really seem to matter what happens to Bill Haskell after that experience. I took what he took from it.”

Interviews From 2014