The new TV drama “The Sinner” premiered on the USA Network Wednesday night. It’s a dark tale about a new mom, Cora (played by Jessica Biel), who murders a stranger on a beach.

That’s not much of a spoiler, since the murder happens in the first episode, and the show is less of a whodunit and more of a “why did she do it”? Over the course of the 8-episode series, a homicide cop (Bill Pullman) will unpack Biel’s initial defense: “ I just did it, and I don’t know why.”

Equally compelling is the question of why USA Network -- the cable network owned by NBCUniversal, a subsidiary of Comcast CMCSA, -0.70% -- is turning to bleaker programming. This grim vibe is a far cry from the network’s previous spate of original scripted shows that are sunny and stylish, upbeat comedy-dramas: “Suits,” “Royal Pains” and “White Collar.”

Ever since USA hit the jackpot with its quirky detective show “Monk,” which ran between 2002 and 2009, the network pursued a formula of effervescent, scripted dramedies to add to the staple diet of movies, reruns and wrestling. Back in 2011, the network’s mantra was “aspirational, blue skies, upbeat, optimistic and character-driven,” Bonnie Hammer, chairman of NBCUniversal Cable Entertainment and Cable Studios, said in a Wall Street Journal article with the headline, “The Happy-Time Network.”

Not anymore. “The Sinner,” for which Biel also serves as executive producer, follows USA’s edgy, cyber-thriller success “Mr Robot,” which returns for a third season in October. The network has also greenlit upcoming gritty shows “Damnation,” a 1930s vengeance drama starring Killian Scott and Gabriel Mann, and “Unsolved,” a true crime series investigating the deaths of rappers Tupac and Biggie Smalls.

USA Network didn’t comment on any shift in their content strategy.

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“The Sinner” premiered strongly on Wednesday night, scoring 1.63 million total viewers. But while USA has been the most-watched, ad-supported cable entertainment network for 11 straight years, shows such as “Queen of the South,” “Shooter,” “Suits,” “Playing House” and even “Mr. Robot” all experienced year-on-year ratings decline, according to website TVseriesfinale.com.

The sun-and-smirk formula may have been wearing thin for the shows’ talent as well. Bruce Campbell, who acted in USA spy action-comedy “Burn Notice,” writes in his upcoming memoir “Hail to the Chin: Further Confessions of a B Movie Actor”:

“Networks are filled with hope and cash- initially -- but they can also be prone to wild mood swings as they try to carve out an identity.

“The USA Network is a good example of this. They started with a perfectly plausible “blue sky” concept behind all their shows -- upbeat concepts with attractive people in nice, mostly exterior locations.

“That formula worked great for probably five years…as happens with all things, change came knocking, and soon USA seemed a little tired, doing the same thing over and over. Viewers seemed to sense that this was all a big ‘branding’ thing and began to check out other viewing options.”

Brad Adgate, a media consultant, said it’s about time USA embraced the dark side. “These types of serialized, edgier, darker, celebrity anti-hero shows have become really prevalent on television so I’m surprised it took so long for this show to happen on USA,” he said. “If it is successful, it can put the network in a different direction compared to where they have been.”

Adgate said a thirst for awards glory could also be behind the shift. “’The Sinner’ is the type of drama that gets critically acclaimed and nominated for Emmys and Golden Globe awards and USA hasn’t had too many of them through the years despite how prolific they’ve been in producing scripted dramas,” he said.

“Mr. Robot” won Emmy Awards last year for lead actor in a drama, for Rami Malek, and best music. Before “Mr. Robot,” the last USA show to get an Emmy nomination was drama “Political Animals” in 2013.