Traveling with strangers can be hard, but traveling with strangers and a murderous alien parasite proves considerably worse in “The Passenger.” This sharply executed, good-humored horror opus represents a promising first dual directorial effort for Fernando Gonzalez Gomez and Raul Cerezo, each of whom has a number of shorts under his belt. While not quite a slam-dunk, it’s more than skillful enough to please genre fans looking for a fun ride, and to raise expectations for their next collaboration (“Viejos,” aka “The Elderly,” another horror already in post). Dark Star and Bloody Disgusting are releasing to limited U.S. theaters on June 3, with VOD and DVD release June 28.

The requisite “first victims” prologue finds two English-speaking backpackers on a rural road having an alarming encounter with a ghoulish woman in a silver red-carpet dress. Then we meet Blasco (Ramiro Blas), a middle-aged man who’s purportedly had past professional lives in the bullfighting and rock-band milieus. But now he’s living off the beloved if somewhat decrepit old camper van he calls “Nella” as a driver for hire. His customers today are all women, which is a tad unfortunate, since Blasco is the kind of swaggering macho blowhard prone to say things like “Brute strength is a man’s job” as he grabs a passenger’s luggage.

He’s already irked Mexican visitor Mariela (Cecilia Suarez), a nurse on a trip of some personal urgency, when their company expands with the addition of uptight upper-middle-class Lidia (Cristina Alcazar) and sulky teenage daughter Marta (Paula Gallego), who are immediately at each other’s throats. Marta, we eventually learn, is being delivered to her divorced father’s distant house while Mom works abroad, something she interprets as just another in a long line of parental abandonments. Nor can garrulous Blasco keep his trap shut long enough to avoid exacerbating such tensions.

Just when it seems we’ll be stuck with four equally irritating, bickersome characters, however, Luis Sanchez-Polack’s script surprises by imbuing them with some sympathetic depth. Seated behind a clear plastic partition, the two older women share confidences that expose some hard knocks of experience. In the front, caustic teen and skeezy dude four times her age likewise find empathetic common ground.

Thus, against initial expectations, we’ve come to quite like these people by the time night falls, and the back road Blasco has taken to avoid tolls fatefully leads to a lone figure standing in the middle of nowhere. Hit head-on, that person is nonetheless still alive, the passengers insisting she be driven to the nearest hospital. This accident stirs another argumentative storm, so the other three fail to notice until it’s too late that their new passenger (being tended to by Mariela in the rear) is not, in fact, a person anymore — but rather something related to the possible UFO crash site they’d stumbled upon some hours earlier. This E.T. is not cute or nice, and it can assume the form of any unfortunate “host” it attacks.

The clever screenplay keeps coming up with new ways to escalate the crisis, while the directors are equally deft at staging both the violent action and persistent verbal spats between stubborn characters. A particularly resourceful contributing factor is Ignacio Aguilar’s widescreen cinematography, which calls upon a variety of techniques, from deep-focus shots to diagrammatic overhead ones that are attention-getting yet always purposeful. (Incredibly, this is his first feature as DP.) Indeed, “The Passenger” is well above average in all design and tech departments. They help it arrive at a colorful, atmospheric, slightly cartoonish tone that stops short of outright horror comedy, but is not entirely to be taken seriously either.

The piling-one-emergency-atop-another structure — always a tricky thing to sustain — does begin to pall in the later going as inspiration tapers off a bit. This winds up being a film more giddily entertaining in the moment than memorable in sum effect. But the actors are very good, editor Sergio Rozas’ input acute, and Alejandro Roman’s original score runs a useful gamut from Pino Donaggio-type florid suspense to a neatly jazzy final-credits track. “The Passenger” doesn’t quite transcend its basic creature-feature premise, yet it does make getting to a familiar destination more fun than many a similar enterprise has managed.