The first half of Julia Loktev’s second feature film, The Loneliest Planet, is a dazzling tour de force, as young lovers Alex (Gael García Bernal) and Nica (Hani Furstenberg) revel in all that life has to offer. Shortly before getting married, they have decided to go on a hiking trip through the Caucasus Mountains in Georgia, led by a guide named Dato (real-life mountaineer Bidzina Gudjabidze, in his first acting role). Alex and Nica are fresh and alive, their eyes filled with wonder, their faces in perpetual, infectious smiles as they make their way through spectacular landscapes gorgeously photographed by cinematographer Inti Briones. In several shots, the three hikers are barely visible walking in the distance as Briones focuses on breathtaking views of the lush green mountainside and vast Central Asian landscape (as well as, in close-up, Furstenburg’s dazzling red hair). What little dialogue there is doesn’t really matter; in fact, much of it is hard to hear, more like background noise, and what is spoken in foreign languages isn’t even translated. But when the travelers run into three locals, something happens that upends the dynamic and severely changes the relationship among Alex, Nica, and Dato, something that requires the kind of split-second decision that one can never take back, resulting in a return journey that is much darker, the smiles, laughter, and romance disappearing in a stark moment. Based on Tom Bissell’s short story “Expensive Trips Nowhere,” The Loneliest Planet recalls such seminal works as Mikhail Kalatozov’s The Letter Never Sent, Andrei Tarkovsky’s Stalker, John Boorman’s Deliverance, Akira Kurosawa’s Dersu Uzala, and Roberto Rosselini’s Voyage in Italy, in which location serves as a character of mystery and potential danger. Loktev, a visual artist who previously made the 1998 documentary Moment of Impact, which details her family’s very personal experiences after her father was hit by a car, and her 2006 narrative debut, Day Night Day Night, about a female Palestinian suicide bomber, has crafted a mesmerizing tale built around small subtleties and the tender, fragile nature of human relationships, in which one misstep can have shattering consequences. Mexican actor García Bernal and New York-born Israeli star Furstenberg make a terrifically believable couple, so vibrant in the first half, so tentative and subdued in the latter sections.