If its first episode, “Fantasy Land,” which aired Sunday, is any indication, Entourage’s fifth season will be veering off its beaten track and exploring new styles and storylines. The premiere suggests the HBO series is evolving in terms of tone and character development. New approaches, coupled with the show’s characteristic charm and humor, could produce the sharpest season yet.

Thanks to the writers’ strike of 2007, fans had to wait a whole year to learn what became of actor Vince Chase (Adrian Grenier) after his dream film project bombed at the Cannes Film Festival. This season opens with a segment of “At the Movies with Ebert & Roeper,” in which critics dub Vince’s project one of the year’s worst movies. Their scathing criticism sets a tone of failure and regret for the episode.

After watching the review, Vince’s best friend and manager, Eric “E” Murphy (Kevin Connolly), voices guilt over the film’s failure to Vince’s brother, Johnny “Drama” Chase (Kevin Dillon). Though it’s laced with classic “Entourage” humor, the scene is surprisingly troubling and feels uncharacteristically somber. The subtle complexity of the scene shows an intriguing tonal departure from the humor of past seasons.

Vince copes with failure by running away, an approach viewers have seen him take in previous seasons. While Drama and E remain in Los Angeles, Vince and the crew’s fourth member, Turtle (Jerry Ferrara), escape to a veritable Mexican paradise where they can drown their sorrows in tequila, jet skis and scores of luscious Mexicans.

While the scenes of illustrious partying are standard fare for “Entourage,” the group’s separation is not. In a show that has developed around strong bonds of friendship and male camaraderie, it seems strange to see the

entourage scattered across the globe. Though they do reunite before the end of the episode, their initial separation may indicate the characters’ individual storylines will play more significant roles this season.

And, of course, “Entourage” just wouldn’t be the same without Vince’s high-powered, high-strung agent, Ari Gold (Jeremy Piven). From the moment he enters the screen, Piven’s performance takes over. After his first appearance in the episode, it becomes apparent that Ari has lost none of his hilarious intensity.

Season five could make for a much darker “Entourage” — never before in the series’s run has Vince’s career looked so grim. Though he eventually agrees to leave his island paradise and reclaim his name in the real world, Vince has yet to shake the gloomy sense of defeat that hangs over him. The true driving force behind this season is going to be Vince’s fight to gain back what he’s lost.

But fear not — a rougher, grittier “Entourage” can still be fun. This notion is driven home by the episode’s delightful conclusion, in which Johnny and his golf club inflict some serious property damage on an enemy’s car. As they watch Drama smash a windshield with a familiar anarchic glee, fans can rest assured: No matter what’s in store for the boys from Queens, it’s going to be wild.

“Entourage” airs at 10 p.m. Sundays on HBO.