“Star Trek: Picard” is a sequel to “Star Trek: The Next Generation,” but it is NOT just a continuation of the 1987-94 series.

If you go into “Picard” expecting to see Episode 179 of “Next Gen,” you’re going to be terribly disappointed. It’s a very different show. (It starts streaming Thursday on CBS All Access, one episode each week.)

And before anybody starts criticizing the producers of “Picard,” remember Sir Patrick Stewart is one of them. And he demanded that the new series be very different or he wouldn’t return in the title role.

It’s been 17 years since we last saw Jean-Luc Picard (Stewart) in “Star Trek: Nemesis,” the fourth and final “Next Generation” theatrical film. The character is not only older (Stewart is 79), he’s angry and bitter. After a major falling out with Starfleet (shown in an Episode 3 flashback), Picard has retired to his family vineyard, where he spends his time with his dog, Number One, and two Romulan aides (Evan Evagora and Harry Treadaway), who are more than they appear.

Picard is still mourning the death of Data (Brent Spiner) in “Nemesis,” and his anger at Starfleet and the Federation is rooted in the destruction of Romulus in the 2009 reboot movie “Star Trek.” (Remember, the timelines of the reboot films and the rest of “Trek” didn’t diverge until after Romulus was destroyed.)

Picard’s closed-off existence is interrupted by the sudden appearance of a young woman (Isa Briones) seeking his help. He doesn’t know her ... or does he?

Without spoiling anything, Picard is soon joined by a scientist (Allison Pill); a former Starfleet subordinate (Michelle Hurd) with a substance-abuse problem; and an ex-Starfleet officer (Santiago Cabrera) who, fortunately, pilots his own ship. And he sets off to save the galaxy ... again.

(Spiner appears in the series — no spoilers about how. And Jonathan Del Arco shows up as former Borg drone Hugh, a role he played in two episodes. Later in the season, we’ll see Jonathan Frakes as Will Riker, Marina Sirtis as Deanna Troi, and Jeri Ryan as Seven of Nine from “Voyager.”)

“Picard” owes a lot to “Star Trek: Discovery.” It’s one big story broken into 10 chapters. It’s dark and disturbing, and blows up our long-held beliefs of what Starfleet and the Federation stand for.

There hasn’t been an apocalypse, but “Picard” has an almost post-apocalyptic feel to it.

When I attended the Hollywood premiere of “Picard” — the first three episodes were screened at the Cinerama Dome, with Stewart and a slew of past and present cast members in attendance — the biggest crowd reaction came at the end of Episode 3, when Picard finally leaves Earth and utters one of his catchphrases. (Well, catchword.) The fans hooted and cheered the moment that felt most like the Picard we loved three decades ago.

But it’s just a callback to “Next Generation,” designed to delight Trekkers. If you’re hoping to see Picard back in uniform, you’ll have to reset your expectations.

And that’s not a bad thing. Three episodes in, there’s enormous reason to be excited and optimistic about “Star Trek: Picard.” It looks like a superior drama, and I can’t wait to see what happens next.