Jared Harris says 'Mad Men' costar Jon Hamm showed him the importance of 'looking after the other actors' on a show where you're the lead

• Jared Harris said he brings lessons from "Mad Men" to every project where he's the lead.
• Harris played advertising executive Lane Pryce for three seasons on the period drama.
• "I admire the way that Jon Hamm led that company, I took those lessons on board," he said.

Jared Harris wowed "Mad Men" viewers with his moving performance as Lane Pryce. Although it's been almost a decade since his character's last appearance on the show, Harris said his time on "Mad Men" has influenced every project where he's the lead.

While speaking with Insider about his new AMC show "The Beast Must Die," Harris spoke warmly about his former costar, "Mad Men" lead Jon Hamm.

"I admire the way that Jon Hamm led that company," Harris told Insider. "I took those lessons on board when I've been the number one on the show - that you have responsibilities, that you must look after the other actors and you must make sure that you're their advocate."

He added: "You must speak up for them if you can - if they need your help. And then, you look out for each other. You make sure that you're going to be able to do the best work that you can do."

"Mad Men" aired for seven seasons, from 2007 to 2015, and followed people working at advertising agencies in the '60s. The critically-acclaimed series' ensemble was led by Hamm's charismatic advertising executive, Don Draper.

Harris played Draper's tragic coworker, Lane Pryce, for three seasons.

Now, Harris leads "The Beast Must Die," which tells the story of Frances Cairnes (played by Cush Jumbo), a woman trying to track down the person who killed her young son in a hit-and-run accident. Her search for answers leads her to the home of George Rattery (played by Harris).

While Pryce doesn't always make the right choices on "Mad Men," he's ultimately someone viewers sympathized with. But it's hard to feel similarly about Harris' "Beast" character, George.

From his very first appearance on-screen, George is a deeply unpleasant character who is cruel to those around him - and Harris leans into that villainous portrayal.

"George doesn't care about anybody," Harris told Insider about his "Beast Must Die" character. "George is a narcissist and he only cares about how you make him feel about himself. If you make him feel good about himself, then he likes you and you're worthwhile to him."

"If you don't make him feel good about himself, then he doesn't have any use for you," he added.

Here's a sneak peek at the upcoming third episode of "The Beast Must Die"

"The Beast Must Die" airs Mondays at 10:00 p.m E.T. on AMC, with new episodes premiering a week ahead on AMC+.