Here’s why Det. Ambrose has insight into Cora’s case.

[Editor’s Note: The following contains spoilers through Episode 6 of “The Sinner.”]

Although “The Sinner” is bent on discovering why Cora Tannetti (Jessica Biel) stabbed a stranger to death out of the blue, another storyline has captured the attention of viewers beyond that central mystery. The USA Network limited series also centers on Harry Ambrose (Bill Pullman), a detective determined to get to the bottom of Cora’s case.

In the Petra Hammesfahr crime novel from which “The Sinner” is based, the detective on the case is fairly generic and not very interesting. This is a far cry from the series’ Det. Ambrose, whose private life is far more colorful than that of the typical embittered detective stereotype. In fact, his character is one of the most brilliant deviations from the novel.

All credit goes to the writers and also to Pullman himself, who embodies Ambrose with a quietly unapologetic tenacity. No matter what the situation, Pullman is able to give Ambrose a bit of a glint in his eye and half-smile. It’s both unsettling and comforting all at once considering that he’s often discussing a brutal murder. That, coupled with a seriously impressive salt and pepper beard, are the physical reflections of the complex man underneath.

Because, of course, Ambrose also has a secret, and it’s one that contributed to the breakdown of his marriage: He’s been seeing a dominatrix named Sharon (Meredith Holzman) on the side. This infidelity tarnishes his reputation in the eyes of the viewer, making him imperfect and therefore somewhat relatable. It also gives him an oddball quirk that is in keeping with the colorful personalities that have been introduced in Cora’s family.

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Ambrose is in denial that this is anything more than a penchant for kink or merely letting off steam. It becomes rapidly clear to viewers that this has evolved into an addiction. Not only did he lose his wife over it, but he’s also losing himself in the activity to the point of endangering his own life. Even Sharon has become disturbed by how Ambrose will neglect to communicate with her during play, thus making it difficult for her to know when to pull back on the roughness.

Read More:‘The Sinner’: Why This Mystery Is Swapping Out Red Herrings for Something Much More Satisfying

This dark pull gives him an intuition about Cora and what may drive her. While many other detectives would’ve dropped the case once she pleaded guilty to murder, Ambrose knows that the answers to why Cora killed someone is important and deeply rooted. Perhaps its his own denial that recognizes that her psyche is in denial about a prior trauma. Or maybe he just understands when someone is slightly twisted for whatever reason.

More than that though, both Cora and Ambrose have lost control. The detective is a slave to his desires and need for oblivion, while Cora has been enslaved by the guilt that has been ingrained in her since childhood through her mother and sister Phoebe (Nadia Alexander). As we’ve seen in Episode 6, this leash tightened even more with the emotional and sexual abuse Cora has been subjected to.

“The Sinner” is poised to reveal all of Cora’s secrets soon, but while this will provide some relief and allow her to reclaim some of her autonomy, she’ll no doubt still need to work out her feelings about it all. Since Ambrose’s character has been a creation wholly unique to the series, there’s no guarantee he’ll reach a parallel epiphany about his issues, but perhaps he’ll be inspired to try therapy since it worked so well on Cora.

“The Sinner” airs Wednesdays at 10 p.m. ET on USA Network.