Like the bottomless trunk totted by “magizoolologist” Newt Scamander, “Fantastic Beasts: The Crimes of Grindelwald” is a mixed bag of wonders.

Newt (Eddie Redmayne) can reach into his suitcase and, like Mary Poppins before him, pull out just about anything. And it sometimes feels as though J.K. Rowling — a screenwriter here for the second time — is similarly infatuated by her unending powers of conjuring. In this overstuffed second film in the five-part Harry Potter prequel series, every solved mystery unlocks another, every story begets still more. Narratives multiply like randy Nifflers (one of the many species of creature in Newt’s bag).

The usual problem for spinoffs is their thinness or their unfulfilled justification — especially ones that stretch an already much-stretched tale. (There were eight Potter movies.) But neither are issues in the two “Fantastic Beasts” films, each directed by former “Potter” hand David Yates. Both movies are rooted in purpose. “The Crimes of Grindelwald,” especially, is an impressively dark and urgent parable of supremacist ideology aimed squarely at today’s demagogues of division. And neither film lacks in density of detail, character or story.

No, the only real crime of “Gindelwald” is its sheer abundance. In zipping from New York to London to Paris (with ministries of magic in each locale), this latest chapter in Rowling’s pre-Potter saga feels so eager to be outside the walls of Hogwarts (which also get a cameo) that it resists ever settling anywhere, or with any of its widely scattered characters — among them Newt, the conscientious dark magic investigator Tina (Katherine Waterston), the New Yorker no-maj Jacob (Dan Fogler), Tina’s sister and Jacob’s sweetheart Queenie (Alison Sudol) and the haunted former schoolmate of Newt’s, Leta Lestrange (Zoe Kravitz)

No one does the foreboding sense of a looming battle better than Rowling. Now, it’s the rise of Gellert Grindelwald (Johnny Depp), freshly escaped from prison, who casts a lengthening shadow over the land. With a blond shock of hair and a ghostly white face, Grindelwald is Rowling’s magical version of a white nationalist, only he believes in the elevation of wizards — “purebloods” — over those who lack magical powers, or “no-majes.”

It’s 1927 and the dark clouds of fascism are swirling; World War II feels right around the corner. In one the movie’s many tricks, Grindelwald drapes Paris in black fabric, like a wannabe Christo.

Despite the gathering storm, the pacifist Newt (Redmayne, cloyingly shy), resists drawing battle lines. When pushed by his brother Theseus (Callum Turner), who like Tina is an “Auror” who enforces magic law, Newt responds: “I don’t do sides.”

The events of “The Crimes of Grindelwald” will test Newt, just as they will anyone trying to follow its many strands. The hunt is on for at least three characters — the missing Queenie, the on-the-lam Grindelwald and Credence Barebone (Eza Miller), the powerful but volatile orphan who spends much of the film seeking answers to his identity. He’s the Anakin Skywalker of “Fantastic Beasts,” whose soul is fought for by both sides.

If all of this sounds like a lot, it most definitely is, and that’s not even mentioning Jude Law joining in as a young Albus Dumbledore, who turns out to be awfully roguishly handsome under that ZZ-top beard. But our time here with him is short, just as it is with so many characters who — to the film’s credit — we yearn for more of (Fogler’s Jacob, especially). There is a flicker of a flashback that hints at a long-ago, maybe-sexual relationship between Dumbledore and Grindelwald; it would be the film’s most intriguing revelation if it wasn’t merely baited for future installments.

Siblings are everywhere in “The Crimes of Grindelwald.” Just as in the houses of Hogwarts, Rowling delights in duality and the interplay of light and dark. Even within the Aurors there are competing methodologies of law enforcement to face the growing threat. Newt is carried along like an avatar of sympathy: he believes that every beast can be tamed, that every trauma can be healed.

Rowling’s only source material going into the “Fantastic Beasts” films was a slender 2001 book in the guise of a Hogwarts textbook. But she has, with her mighty wand, summoned an impressively vast if convoluted world, one that’s never timid in exploring the darkness beneath its enchanting exterior. And, with Yates again at the helm, “The Crimes of Grindelwald” is often dazzling, occasionally wondrous and always atmospheric. But is also a bit of a mess. Even magic bags can be overweight.

“Fantastic Beasts: The Crimes of Grindelwald,” a Warner Bros. release, is rated PG-13 for some fantasy action violence. Running time: 134 minutes. Two and a half stars out of four.