It was supposed to be a somber scene in “Mary & George,” the Starz limited series about an opportunistic Jacobean widow (Julianne Moore) who maneuvers her second-born son, George (Nicholas Galitzine), into the corridors of English power. The moment called for Moore, as Mary, to toss a handful of dirt into the camera lens and onto the casket of her late, abusive husband. But it seems Moore, while one of the best actors around, doesn’t have particularly good aim.

“I’m definitely not an athlete,” Moore said in a recent video interview. “They were like, ‘Just throw it on the coffin.’ When I threw it, it [went off to the sides] like a clock: 12 o’clock, 3 o’clock, 6 o’clock, 9 o’clock. It was so sad.” But also funny enough to give cast and crew a case of the giggles. “Everyone just burst out laughing,” Galitzine said in a separate interview. “She took one handful of soil, and it missed north of the camera. She took another one, threw it, missed south of the camera; two more, one west, one east. And we just could not keep it together. It was just a perfect cross of unathleticism.”

Inspired by Benjamin Woolley’s nonfiction book “The King’s Assassin: The Secret Plot to Murder King James I,” “Mary & George” can get quite macabre as it dramatizes the Machiavellian scheming and bloodshed behind the rise of George Villiers, engineered by his mother, Mary. Which didn’t prevent Moore and Galitzine from having a blast making it. Modern and lurid in its sensibility — this is very much a show for grown-ups, with sex and violence aplenty — “Mary & George” offered more than enough to fire the imagination of its cast.

Starting with the first scene, in which Mary reacts with a combination of resignation, scorn and love to the birth of her second child (his birth order appears fated to ensure his lack of potential), Moore was drawn to the language used by writer-producer D.C. Moore (no relation). “The way she speaks about her child and his lack of possibilities, it’s funny and it’s outrageous, and also strangely tender,” the actor said. “What D.C. did with the language was just modern, forthright and funny, and arresting. There was a heat to it and a directness and a kind of profaneness that I thought was interesting.”

Mary ends up steering George into the court of the sexually voracious King James I (Tony Curran), whom he seduces on his way to gaining power and influence in diplomatic affairs. Rising from their low station, mother and son trample over propriety, make a lot of people angry and even leave a few bodies in their wake. It’s a rags-to-riches story in which the rags are soaked with blood.

Like many ambitious operators through the ages, Mary makes a path where there is none.

“She’s a person with no agency and no autonomy,” Moore said. “There’s nowhere in her life that’s her own. Any of her agency is through either the men that she’s married to or her male children. This is a woman who came from a middling family and didn’t have a whole lot of luck with her marriages but managed to position her children really well and be buried in Westminster Abbey.”

For all its skulduggery and eventual consequences, “Mary & George” also has a wicked comedic bite, especially as young George finds his footing in the king’s court and aims for the royal bedchamber. “It’s a show that changes quite drastically in genre as it goes along,” Galitzine said. “It starts off with a level of bounce to it and it’s very comedic. And then as the stakes grow, and as Mary and George ascend to power, it becomes much more of a drama than a comedy. It’s a dysfunctional family, and then the royal court is equally dysfunctional, and the king is even more dysfunctional.”

For all the poisonous plotting they shared, Galitzine enjoyed a warm relationship with his onscreen mother.

“Julie is very giving,” he said. “She always has ideas about everything. She’s very knowledgeable about all the realms of an acting performance, whether it’s emotional or physical. Her command of film IQ is impeccable. She’s just an incredibly kind person, as well as being immensely talented. She brings levity to the working day, despite doing really intense pieces of acting.”

And when the dirt went flying, she took it in stride.

“That just humanized her in such a wonderful way,” Galitzine said.