You want to know why I still watch “Grey’s Anatomy”? Check out last week’s episode on demand.

In it, Shonda Rhimes and Co. pull off muscular – and affecting – drama around a plot point the showrunner planned at the series’ inception 11 years ago. That’s remarkable enough, but the episode titled “Only Mama Knows” also showed, in starker detail than before, the price a talented woman paid for her ambition and skill.

This has been the central conflict of the show: Can an ambitious woman have it all? What if she doesn’t want to be a mother? Or the men in her life can’t handle her talent or ambition?

Meredith Grey, the show’s title character, has struggled with this, and the shadow of her gifted mother, Ellis Grey, from the start. It’s a major flashpoint in her marriage to fellow surgeon Derek Shepherd (Patrick Dempsey).

If this were a more conventional series, Meredith (Ellen Pompeo) might be depicted as an anomaly. But Rhimes, a supremely talented showrunner and Dartmouth grad that also created “Scandal,” knows that smart and ambitious women aren’t as rare as unicorns.

From the start, doctor in training Meredith had an equally, if not more, ambitious pal in Cristina Yang (Sandra Oh), even less interested in conforming to gender stereotypes than Meredith.

And there was, and still is, Bailey (Chandra Wilson), a stern taskmaster for newbie doctors, plus telling flashbacks of Ellis (Kate Burton, left) in her prime. Nominally softer female characters such as Izzie (Katherine Heigl) were shown to have overcome long odds in their quest to become a doctor.

And now, 11 episodes in, Meredith is coming to terms with the love child her late mother had with Richard (James Pickens Jr.) but Meredith somehow did not know existed. When this development was first revealed late last season, long-time viewers could be forgiven an eye roll.

I know I certainly did.

After all, another sister of Meredith (from her father’s subsequent marriage) had already come and gone. And episodes had grown slack with an attenuated send off to Oh’s Cristina. I was still watching, but less avidly.

“Grey’s Anatomy” had certainly tested my faith before, most strongly with the Denny ghost storyline, but last season’s malaise felt different, more attributable to the show’s age. Another sibling seemed like a tired rehash of the Lexi (Chyler Leigh) storyline.

This sisterhood, however, is pricklier, and a lot trickier to pull off than that one. How could Meredith not know about her mother’s love child? Or Richard? Here, the show’s longevity pays off: The drama plays on viewers’ knowledge of Meredith’s relationship with her mother, before and after Alzheimer’s diagnosis, and the cloudiness of memory.

With this episode, Rhimes serves notice that she is not yet done examining the fallout from female ambition. “Only Mama Knows” is especially delicious coming so soon after the Alessandra Stanley’s reductive story about her “angry characters” in the New York Times. How many times are strong and ambitious women painted with that brush? Too many.

Ellis’ story is haunting, but Rhimes’ prognosis for contemporary women doesn’t seem nearly as bleak. For starters, she has created a mini-empire while raising children, and bristles when media press her on work-life balance.

And this week’s episode suggests that the long battle between Meredith and Derek over dueling career ambitions and parenthood isn’t as hopeless as it was starting to seem.

Maybe, just maybe, this fictional woman can really have it all.

This being a Shonda Rhimes concoction, I’m certainly not expecting a happily ever after ending for “Grey’s Anatomy,” however. The episode itself ends on a bittersweet note that I will not spoil here. You really should watch for yourself.

For more on Rhimes, read THR’s recent cover story , and its story about how this week’s remarkable episode came together. Mark Harris also wrote a compelling story about the “angry black woman” flap for Grantland.

And here’s my review for Rhimes-produced “How to Get Away With Murder,” which has yet to capture my fancy.

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