There are so many TV shows arriving and returning every day that it’d be easy for a little-known drama like “Happy Valley” to get lost in the shuffle. But thanks to an exceptional lead character — and the even more impressive actress, Sarah Lancashire, portraying her — this U.K. cop series should definitely light up the radar of discerning viewers.

It’d actually be worthwhile to check out the first season of the program — which, like the second, is on Netflix in the U.S. — before the plunging into the newest batch of episodes. Season two has several important links to events in the six hours that constitute season one, and it’s easily consumed in a couple of sittings.

Well, “easily” may not be the right adjective. “Happy Valley” is unpretentious and by no means humorless, but it goes to some dark and difficult places (and the characters’ Yorkshire accents make some lines hard to decipher, though meanings are usually clear from context). In both seasons, murders and other acts of violence become part of the psychologically astute narratives, and the central fact of police officer Catherine Cawood’s life is that her daughter committed suicide after being raped. The fallout of that tragedy affects Catherine every day in a number of ways, though she tries hard not to let it influence her brisk approach to her job.

Like the show she so capably stars in, Lancashire never goes to exploitative or melodramatic places in her portrayal of the character. “Happy Valley” is unfussy and matter-of-fact, but it’s also very perceptive about pain, regret and human nature. The show’s curiosity about what motivates decency — and what accounts for its absence — ends up giving it a quiet but unshakable power, and its sensible and straightforward vibe lends dignity to what is, at its core, a tale of stoic endurance.

Stoicism is certainly a way of life in the Yorkshire town where Catherine has been a police officer for many years. Crimes can involve purloined sheep and low-level drug dealing, and she often knows the people she’s arresting or questioning. This easy familiarity with her community, and the fact that she sees their everyday struggles is part of what makes her effective: People tend to trust her. When she goes to warn some local prostitutes about the existence of a possible serial killer, she brings them sandwiches, and her sincere regard for them is obvious. They like Catherine, and there’s no judgment in her treatment of them.

Catherine’s warmth and wry kindness are also on view in her conversations with her ex-junkie sister, Clare (Siobhan Finneran), who lives with her. Even more so than last season, the scenes between the sisters form the show’s emotional backbone. Lancashire and Finneran have a terrific rapport, and creator Sally Wainwright has a real knack for writing sibling dialogue that feels unforced and realistic.

Clare is a recovering addict, and the shadows of co-dependence that lurk between the women is one of “Happy Valley’s” more interesting subtexts. But there are many complicated strands in this efficiently paced drama, to the point that one wishes each season were just a bit longer, if only to give performers like Finneran even more to do.

That said, the focus on Catherine is understandable. It’s hard to think of a scripted female character who is more complicated and fascinating (though the women played by Julianna Margulies, Kerry Washington and Keri Russell are in Catherine’s league). She’s instinctively giving and often selfless, but she can also be stubborn, abrupt and prickly, and can freeze people in their tracks with a bone-chilling glare of suspicion.

And yet Lancashire’s empathic performance makes it easy to see why Catherine loses her patience at times; she’s still wrestling with the consequences from the attack on her daughter, not least of which is the young son her daughter left behind. Sometimes Catherine’s impetuousness leads her to make bad decisions, but there’s no doubt her family and parts of her community would be far worse off without her occasionally annoyed but tenacious devotion to them.

Catherine is, on some level, still simmeringly furious, as well as sad; when not wearing her police-issue coat, she goes around in a shapeless parka that she wears like a shield. A woman who doesn’t hide her anger can make other people very nervous, and “Happy Valley” isn’t shy about confronting that idea. There are a lot of discussions about whether Catherine is nice enough, which is not a conversation Vic Mackey ever had to have on “The Shield.” But “Happy Valley” is realistic about how a shrewd, implacable female cop would be viewed when she’s not in a charitable mood. It’s rare, not to mention refreshing, to come across a female TV character who is not defined by her relationship with a man, and who is so well developed that even when she’s abrupt or making questionable decisions, she’s always fascinating and believable.

Finneran is a refugee from “Downton Abbey,” and “Happy Valley” recruited another member of the Earl’s staff this season: Kevin Doyle, the unfortunate Molesley on “Downton,” plays a hapless detective who ends up in a nightmarish situation of his own making. James Norton, so compassionate in the period drama “Grantchester,” once again shows his terrific range as Tommy Lee Royce, a hardened criminal with a deep reservoir of toxic self-pity. There are a couple of supporting characters in the first half of season two — a woman who’s been drawn into Tommy’s orbit and another who is having an affair with Doyle’s character — who are a somewhat one-dimensional. They only stand out because they’re not as well-rounded and instantly interesting as most characters in this drama, which gathers up and knits together a few different criminal investigations as the season progresses.

In the main, however, “Happy Valley” does a fine job of conveying what it’s like to be a small-town police officer whose daily rounds allow her to confront the dumb, silly and awful things people do to each other, and to wrestle with what she herself is capable of. Very little shocks her, but she still manages to surprise herself — in ways both good and bad.