★★★★☆

“How to Train Your Dragon: The Hidden World” is a visually stunning exploration of what it means to grow up, complete with the fire-breathing companions that made the first two films in the series so compelling.

“Hidden World,” directed by Dean DeBlois, opens amid dark fog as protagonist Hiccup, voiced by Jay Baruchel, works to free dragons caged by captors with his ragtag band of friends and loyal pet dragon Toothless, the last night fury.

The raid quickly devolves into juvenile antics as one of the group members accidentally sets himself on fire and another brings a baby dragon to the fight because he could not find a sitter. This opening scene sets the tone for the rest of the film, weaving lightheartedness throughout an unexpectedly solemn tale, setting the final installment slightly apart from the rest of the “How to Train Your Dragon” series.

With Hiccup as their new chief, the human inhabitants of the Isle of Berk, who once disdained and feared dragons, now welcome them as beloved pets. As Hiccup brings more and more rescued dragons back to Berk, however, this chaotically colorful dragon paradise becomes a target for those who wish to exploit and kill these winged creatures.

When Grimmel, voiced by F. Murray Abraham, a villain whose main source of pride is exterminating dragons, sets his sights on Toothless, Berk faces its greatest danger yet. Hiccup, still settling into his role as chief, decides to relocate his people to the mythical home of dragons, rumored to sit at the edge of the world. Only in this Hidden World, he insists, can dragons and Berkians coexist without human interference and violence.

Hiccup’s personal development has consistently been central to the trilogy as he navigates the thorny process of growing up — a journey even more complex for a Viking prone to pacifism. His mentor Gobber, voiced by Craig Ferguson, impresses upon him in “Hidden World” that the youth are supposed to lead Berk into the future, calling on a familiar generational habit of imposing the pressure of progress on the shoulders of young people that can be seen today.

Hiccup’s anxieties about leadership plague him as he tries to prove himself capable of protecting those he loves. He once again relies on his characteristic optimism rather than heeding the pragmatism offered by the people around him. Hiccup’s insistent pursuit of the Hidden World, a legend told to him as a child by his father, reveals the fundamental difficulties of growing into an adult and having to leave childhood behind.

The relationship between Hiccup and Toothless captures the heart of the movie, providing the same emotional backbone it did for the previous films. Many pet owners will undoubtedly recognize the amorphous bond between the two that seems to fluctuate between that of close friends, siblings and often even a parent and child — it is a relationship that has endeared viewers to the franchise from the beginning and one that only grows more meaningful and heartwarming throughout this latest film.

The animation features significantly in developing their bond. In addition to the picturesque views and vibrant colors of the sky and landscapes, the careful artistry breathes life and nuance into Hiccup and Toothless with its precise rendering of facial expressions and other minute details.

“Hidden World” also explores the codependent tendencies that arise from this relationship: Hiccup cannot recognize his value without Toothless at his side, and Toothless cannot fly without Hiccup to aid him. The film expertly exposes the self-doubt that simultaneously inhibits them and binds them together, forcing the characters to confront their fears.

Toothless even gets his own romantic arc in “Hidden World” when he meets a light fury, a dragon who looks exactly like him except for her pale coloring. His earnest attempts at courtship, including a bizarre mating dance he picked up from another species of dragon, prove to be among the film’s most entertaining scenes. For all the oddness of the dragon mating rituals, his awkward efforts to impress his crush — combined with Hiccup’s endeavor to be Toothless’ wingman — are as charming as they are painfully humanlike.

Unfortunately, the film sacrifices the development of the rest of the characters for that of Hiccup and Toothless. Though the supporting characters provide comic relief and occasionally voices of reason, they have little depth of their own. Most disappointingly, Hiccup’s girlfriend, Astrid, voiced by America Ferrera, who was characterized in the first film as a competitive, headstrong spitfire, is relegated to the role of adviser for Hiccup and never fleshed out much at all beyond her relationship with him.

The primary antagonist, Grimmel, similarly lacks character work, but his missing background in fact makes him a more effective villain. Unlike the antagonists of the previous films, who hunted dragons either out of fear or to exploit them, Grimmel hunts to kill — and takes great pleasure in it, making him all the more unsettling.

In many ways, “Hidden World” is a story about growing up and letting go. The film is darker than its predecessors, and even the brief moments of comedy interspersed are not enough to counteract its more somber nature. This final chapter of Hiccup and Toothless’ story is a deeply satisfying, emotionally resonant account of their personal growth and triumphs, unafraid to tackle the difficulty of change.