Born in the 3-D land rush, “How to Train Your Dragon” has never quite shrugged off the bland corporate sheen attached to it from the start. But almost a decade since taking flight in 2010, these movies have made up for their lack of fire with enough sincerity and genuine sense of wonder to sustain a mild but moving trilogy.

“How to Train Your Dragon: The Hidden World” brings the franchise to a close with an affectionate chapter that continues the adventures of the Viking boy-turned-chief Hiccup and his faithful dragon Toothless, a sleek, black kind of dragon called a Night Fury.

In “The Hidden World,” the dragon utopia that Hiccup has built on the Island of Berk, where Vikings once feared and fought dragons, comes under threat from a dastardly dragon hunter named Grimmel the Grisly whose toothy grin resembles a moonlighting vampire with violently retrograde policies on dragon coexistence.

With Berk under attack, Hiccup rallies the Vikings to uproot and flee to a mythical, undiscovered realm called the Hidden World where dragons could live safely away from humankind.

There are two compelling parts of “The Hidden World” that validate it. The first is the courting scene between Toothless and another white (and presumably female) Night Fury who turns up just as Grimmel does. They swoop and swoon through the sky, gliding in the glow of the Northern Lights like a dragon version of “La La Land.”

The second is the film’s terrific coda, which leaps years forward and adds a wider, wistful and more grown-up dimension to what has always been, at its heart, a boy-and-his-dog story, just with wings.

“Dragon” has done a lot of things right along the way. It brought in cinematographer extraordinaire Roger Deakins to add to the rich Nordic atmospherics. (Deakins remains credited as a visual consultant in “The Hidden World.”) And the series deserves credit, too, for building a story around two unimpeded protagonists with prosthetic appendages.

Without much to draw on from the surrounding characters, “Dragon” has always been predicated on that central twosome and the laudable lesson that animals, even fire-breathing ones, aren’t our enemies unless we make them so.

“How to Train Your Dragon: The Hidden World,” a Universal Pictures release, is rated PG by the Motion Picture Association of America for adventure action and some mild rude humor. Running time: 104 minutes. Two and a half stars out of four.