WHAT IT’S ABOUT Sadie Ellis (Katherine Heigl) is a workaholic defense attorney who almost believes, word for word, the ideals of her firm’s “lefty” founder, Isaiah Roth (Elliott Gould), who insists that he has always “stood by someone accused so that he or she would not have to stand alone.” Almost, until her feelings for a client, Billy Brennan (Steven Pasquale) — accused of killing his girlfriend when both were teens — gets in the way.

Meanwhile, Sadie’s colleague Albert Cobb (Dulé Hill) wants the guy to accept a plea deal, and move on with his life. Another colleague, Tiffany Simon (Dreama Walker), is a newbie, and still learning the Isaiah way. But the firm’s other top attorney, Cameron Wirth (Laverne Cox), knows it cold, and knows injustice, too. She’s a self-identified transgender person.

MY SAY The big news with “Doubt” isn’t just reasonably big, but reasonably historic. This is the first prime-time series on a major broadcast network with a transgender person in a leading role playing a trans character. A key word here is “leading” because trans characters in minor roles have also appeared on “Glee” and “Grey’s Anatomy,” while cable (“The Fosters”) and streaming (“Transparent”) have long been in the forefront of trans characters and issues. Cox, of course, was the pioneer on “Orange Is the New Black,” once again the pioneer here.

Big news, but a big deal? Consider that most CBS viewers have never seen “The Fosters” or “Transparent,” and if they had, Freeform and Amazon would have alerted us to that remarkable fact years ago. This is as radically new for them as it is for the trans community.

Cox’s character, Cameron Wirth, quickly establishes that she was once a man, now a woman, and, with that out of the way, gets down to business. She’s a competent defense attorney, with a brisk courtroom style. That she is a trans person is irrelevant, except that it is not, and during summation for her defendant client, says: “Do we see him, or do we turn away?”

More gauntlet than question, that’s addressed to viewers as much as jury. Do we see her and millions of other trans persons, or turn away? “Doubt” insists that we see. So yes, a big deal.

Oh, and by the way, have we even mentioned “Doubt” is another Heigl attempt to escape the long shadow of “Grey’s,” and the lesser one of “State of Affairs”? Her character is first among equals in the ensemble cast, but Heigl also benefits from being part of that ensemble, much as she did in “Grey’s.” This isn’t “State,” where she’s saving the world while trying to save herself. Heigl’s good here, and “Doubt” is better for the fact that the whole enterprise isn’t necessarily riding on her, either.

That could change, but at least “Doubt’s” pedigree hints that the ensemble stays. Co-creators Joan Rater and Tony Phelan earned their TV PhDs at “Grey’s,” where they once ran the show and learned that more is more. More characters mean more stories, more conflict, more drama, more detours.

With a New York setting and all those tangents, “Doubt” probably won’t mind if viewers mistake this for “The Good Wife.” But that would be a mistake. Instead, think of this as “Grey’s” in a courtroom, with a good New York cast, two legends (Gould and Bill Irwin, who plays a judge), a TV star and a TV pioneer. Add some boilerplate workplace/romantic TV tropes, top it all off with a pilot-ending reveal, mix ’em all together, then hope for the best.

At least Wednesday’s episode does make the better case for hope than — apologies in advance for the bad pun — doubt.

BOTTOM LINE Decent courtroom/workplace drama, also a pioneering one.