Outlander star Sam Heughan on that red coat and why he stood shirtless in the river

Sam Heughan truly shines in Sunday's episode of Outlander as his character, Jamie Fraser, swears obedience to the British, begrudgingly fights his former countrymen, and bids farewell to a beloved father figure. Here, the 39-year-old actor talks from Hawaii -- where he recently vacationed but ended up having to remain because of self-quarantine -- about his final days working alongside the terrific Duncan Lacroix, and why it was important for him to a wear a red coat before going to battle against the Regulators.

ENTERTAINMENT WEEKLY: This was such an incredible episode for you.

SAM HEUGHAN: Thank you. I was so excited about this episode and nervous too because I just knew what it meant. We knew that we were going to lose Murtagh in this episode, and he's been such a strong character. And for Jamie, he's the link to Jamie's past in Scotland. He's really his father figure, as well. He's a silent, constant figure, someone that Jamie can rely on who's been there from the very beginning. And for Jamie to be pitted against him was hard enough, but then to lose him was really traumatic.

Let's talk about Jamie having to wear the red coat.

It was something that I pushed for last season. I really wanted to see Jamie stand on the opposite side of his godfather. And to be fighting with the people that he's fought against the whole time? At Culloden, Jamie was fighting for Scotland, fighting for his clan, his family and his freedom. Now he's completely on the opposite side. I thought it would be quite visually arresting. Also, Jamie is a man of honor, a man of his word. To have to go against everything that he stands for to don this uniform .... last season, Matthew B. Roberts told me that Jamie was going to be on the side of the British by leading this militia, so I posed the question, 'could Jamie wear a red coat?' I just thought everything that's happened in his past from Culloden, to Black Jack Randall, to prison and the red coat really represents everything that Jamie isn't. I thought it would be interesting to explore what that would do to him if he had to wear one, and what it would look like. We looked into it. Historically, a militia leader wouldn't have worn a red coat. They had the brocade, obviously, and their hat, and they would wear them to mark them out. But this was more of a power play by Tyrion, wanting to test Jamie's loyalty. I think it really works.

I just was just blown away by how exciting the battle was. What do you recall about shooting that scene in the woods?

Yeah, it's cool because it's very different from the kind of battles we've done before ... traditional highlanders charge, some swords and tartans is what we've seen. Now we're in the age of more modern warfare, though this feels a lot more like guerrilla warfare. I think we all really enjoyed it. And, to be honest, it's something that I think we've done very well in the past but we haven't had much opportunity to do recently, so I think we all relished it. I obviously love the action stuff. It's the first battle, obviously, that really ignited this movement and serves as the build up to the independence.

Mark Mainz/Starz

You showed such a range of emotion in this episode, obviously starting with saying goodbye to Murtagh What was that day like for you to shoot?

Everyone didn't want to say goodbye to Duncan Lacroix. He's such a wonderful human being, a great actor. He's so, so good. He's also a lot of fun and has been a part of our family since the beginning, so none of us wanted to get to that day. The scenes were actually shot over a very long time period of time. We shot the exterior of the tent first, and I actually went back and picked up the interior in the tent on almost the last day of shooting. So it was tough as an actor to juggle that timeline and that arc, but also fortunate that we got to have Duncan around for the whole season. So at least we didn't have to say goodbye to him on one day and never see him again. He was around for most of the season.

Sam, I feel so stupid. It wasn't until I saw in the credits that that was actually Graham McTavish. Did you get a chance to hang with him when he was there?

Yeah, it's great, isn't it? I think that's a nice little Easter egg for fans. They wouldn't expect that. And obviously he's playing an ancestor. They tried to keep it under wraps and very quiet. I think they gave him a different name. I think his name was Mark Rogers on the call sheet, but everyone knew that Graham would back. He was back a couple of days and, yeah, we hung out.

Robert Wilson/Starz

The scene in the river, what does Jamie say in Gaelic and what was that like to shoot? It had to have been cold as hell.

It wasn't that cold, actually. It was a nice day in Scotland. It was a hot summer. He's calling upon Dougal's spirit to be with him and fight alongside him. It's a great tradition that Scots would have before a battle, that you'd call upon your ancestors and your relatives to be by your side when you go into battle. It's interesting that he's calling upon Dougal, but I think he knows that if Dougal were alive, Dougal would understand this is a time when he's needed.

And it's also a tradition to cut your hand?

Yeah, I guess, like a blood oath. Obviously it's easier to do on camera than it is in reality. I'm sure if I'd had to do it for real, I wouldn't be quite so happy about it.

Let's talk about what you are doing in quarantine! You put together a 30-day social distancing work-out challenge to keep folks healthy. Each day, there is a new, free video posted on the My Peak Challenge website. The best thing we can do is to try help in whatever way we can, whether it's to bring some levity or galvanize people to stay healthy and fit. We wanted to do something to help. This was a simple way for us to hopefully bring a little lightness to people as they stay indoors.

Do you need workout equipment?

No. The idea was that wherever you are, you can do this. Hopefully anyone can do these workouts. So if you've not worked out before, or you just need something to distract yourself from the news at the moment, then you can give it a go.

Want to chat about Outlander? Make sure to go to EW's Instagram account Monday at 1 p.m. ET to hear Maureen Lenker and Ruth Kinane talk about all things Fraser!

Related content: