Throughout his career, Christopher Nolan has been making films that double as puzzle boxes; mysteries that unravel with satisfying, precise logic. Toward the end of his 2014 opus Interstellar, an astronaut (Matthew McConaughey) enters a black hole and finds he can manipulate time itself, now manifested as a chamber of memories he can flip through. It’s an epic concept, but also essentially a grander version of a trick Nolan first pulled in 2001 when he made Memento—his second film, an indie smash that vaulted him to the top of the Hollywood heap. Its budget was small, and its story lacked the ambitious sweep that would later define Nolan’s movies, but 15 years after its release, it’s a movie that clearly set the framework for one of modern cinema’s most distinctive directors.

Leonard (Guy Pearce) is seeking to avenge the murder of his wife, who was killed in an attack that also robbed him of his short-term memory. Because of his condition, he’s covered in tattoos to remind him of his mission, and he has pockets full of Polaroids that help him keep track of his friends and enemies. The film immerses the audience in Leonard’s perpetual state of confusion by running backwards: Each scene is followed by whatever happened right before it, proceeding from a murder committed in the first scene through to Leonard’s decision to commit it in the last. It remains a dazzling trick that holds up on repeat viewings, and the chilly precision with which Nolan executed it helped define the indie movies of the aughts, from the time-traveling mathematics of Primer to the high school neo-noir of Brick.

Memento’s trickery echoes the twisty plotting Quentin Tarantino utilized in the ’90s classics Reservoir Dogs and Pulp Fiction, but it feels much more mathematical. As the main plot winds backward, the film consistently cuts to black-and-white segments flowing in the opposite direction, in which Leonard has a paranoid phone conversation in a hotel room and explains the particulars of his condition. At the end of the movie, Leonard leaves the hotel and drives out of town to murder a man he thinks is his wife’s murderer; the black-and-white scenes bloom into color, and it becomes clear that the two ends of the film’s timeline are syncing.

In 1998, Nolan made his debut with the little-seen British crime drama Following, made for just $6,000, which tells a similarly elliptical and twisty tale of criminal intrigue and revenge. Memento, written by Nolan and inspired by a short story by his brother Jonathan, secured a $9 million budget on the strength of his script alone, funded by the now-defunct indie studio Newmarket. It premiered in Europe in 2000, where it was a hit at the Venice Film Festival, and an even bigger one at Sundance the following year, but didn’t secure U.S. distribution despite rapturous reviews. With the support of the director Steven Soderbergh, who talked the film up in interviews, Newmarket eventually decided to distribute it themselves, a risky move that paid off—Memento made a tidy $25 million domestically.

After its U.S. release on March 16, 2001, it was nominated for two Oscars in the Original Screenplay and Editing categories, and although it lost both, it established Nolan as a director to watch. His next project was a remake of the Nordic crime drama Insomnia with Al Pacino and Robin Williams in 2002, before Warner Bros. tasked him with reviving the Batman franchise in 2005, betting big on the hope that an indie director could make the world’s most famous superhero cool again. Nolan succeeded, and he hasn’t looked back since, mostly making widescreen genre epics with huge budgets. Nevertheless, every movie he’s made has one thing in common with Memento: extreme attention to detail.

Nolan has employed that strict framework to pull off dazzling storytelling feats again and again—think of the perfectly-timed dream-within-a-dream heist sequences of Inception, or the showmanship of his Victorian revenge drama The Prestige, which is structured with the practice of an elaborate magic trick. The magic of Memento, at least on first viewing, lies in realizing the intricacy of the plotting, which turns an ordinary neo-noir thriller into a tale of misbegotten revenge. The audience would have no sympathy for Leonard if the story played in proper time—he’s a patsy, an angry, confused man unleashed on local criminals by his manipulative “friends” (played by Carrie-Anne Moss and Joe Pantoliano) who ends up turning on them almost by accident.

But since his story plays in reverse, viewers are just as adrift as Leonard, and only when the credits roll is the totality of his mistakes made clear, not to mention how powerless he was to prevent them. Throughout the film, Leonard talks about Sammy Jankis (Stephen Tobolowsky), a man he knew who had the same condition, whom he paints as a sad fool who couldn’t understand what was going on around him. Eventually we realize that Leonard is Sammy, metaphorically and probably literally, and that Sammy’s tragic tale is just another one that’s become obscured and fudged in his broken brain over the years.

Though Memento deals with tragedy and loss, it keeps Leonard’s wife (played in flashback by Jorja Fox) at arm’s length as a specter haunting her husband, who’s racked with guilt at his inability to protect her. It’s a motif that recurs throughout Nolan’s career, notably with Rebecca Hall’s character in The Prestige and Marion Cotillard’s in Inception (the latter manifests only as a memory who stalks Leonardo DiCaprio’s Cobb through his dreams). That chilliness, combined with the meticulous attention paid to plot, can make Nolan seem a dispassionate engineer who calibrates everything a little too carefully, including his film’s emotional cores. That’s certainly his signature, and it’s one shared by many of the wunderkind directors who came up in Hollywood at the same time.

M. Night Shyamalan worked in more sentimental territory but with the same tight focus on plotting and story twists, a trope that eventually tripped him up after early hits like The Sixth Sense, Unbreakable, and Signs. The Wachowskis, who directed The Matrix (also starring Carrie-Anne Moss and Joe Pantoliano), matched Nolan’s dispassionate precision on a titanic scale, conjuring action among the monolithic cityscapes he’d eventually mimic in Inception. Indie filmmakers like Shane Carruth (who made Primer and Upstream Color) and Rian Johnson (Brick, Looper) built complicated mysteries within low-budget films, adhering to painstaking logic that watchful fans could unpack, ever so slowly, with multiple viewings.

Nolan’s monolithic style marches on—with Batman behind him and the sci-fi majesty of Inception and Interstellar accomplished, he’s now making a World War II film, Dunkirk, that could pose new challenges. But Memento’s DNA will always be present in his movies. Some directors make calling-card films that establish them in Hollywood, then immediately veer off in different directions, be they mainstream or arthouse. Nolan has always stuck his course. Memento is the brilliant Rube Goldberg machine it was 15 years ago, surprising new viewers with its backwards-spooling plot and enchanting rewatchers by holding up under scrutiny. It’s a gimmick, but one that feels philosophically pure—and it’s that rigor that makes it impossible not to anticipate what he does next.