Following the dramatic events of its season 1 finale, Marshals returned at the beginning of October with a high-stakes mission in season 2, which sees Kayce Dutton attempting to rescue his son after he's kidnapped.
That action-packed opening episode sets the tone for the rest of the season, with Luke Grimes telling Radio Times just how physically demanding his preparation was for both instalments.
"Coming into season 1, I didn't realise how much of an action show this would be, and we did training on set every day because every other day there's some action scene with a shootout or clearing rooms as a unit," he explained.
"It's something you have to really work at. And I'd never been part of an action show, so the level of physical endurance to get this job done was a lot more than I thought it would be."
"I quickly realised I had to prepare for that better," he added.
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Grimes was put through his paces by former Navy SEALs and Special Forces officers.
"These guys were in real life, the people that we are trying to play," he said. "It’s awesome to have them around as they’re able to tell us when we’re doing something wrong and how to make it better.
"They’re on set anytime we do anything tactical so it’s a constant learning curve."
The fact that Marshals is filmed in Park City, Utah, which is 7,000 feet above sea level, also made the role more physically demanding.
But it wasn't just the levels of fitness required that tested Grimes. He also wasn't anticipating just how emotionally demanding it would be playing Kayce Dutton, who he described as a "magnet to chaos".
View Green Video on the source websiteThe actor has been able to explore a more vulnerable side of his character after losing his on-screen wife, Monica Dutton, to cancer between the end of Yellowstone and the first season of Marshals.
He has also recently started to open himself up to the possibility of a new relationship following recent developments with Andrea Cruz (Ash Santos).
"For Kayce, something that’s very new is the possibility of romance," said Grimes. "I never saw that coming.
"From the time we learned that Monica had passed away and you’re going to find Kayce without his soulmate, I couldn’t imagine the idea of him opening up to anything romantic with anyone else.
"Now, enough time has passed that it feels right to allow him to explore that a little bit."
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