At last we have a winner. British director Christopher Nolan has made the first truly great film of the year with “Memento.” An immaculate and challenging tale about a man with severe short-term memory loss who attempts to avenge the murder of his wife amid his own hopeless confusion, “Memento” is a transcendent piece of film noir that jumbles conventional storytelling techniques to achieve fantastic results.

Right from the start “Memento” distinguishes itself from the lion’s share of recent films through its stream-of-consciousness filmmaking. The film zooms into the present and back into the past just as the mind interminably does until we understand that we are witnessing much of the movie from the standpoint of one man’s badly damaged memory. Nolan completely inverts the A-to-Z time structure of most films, working chronologically backwards as Leonard tries to uncover the foggy truth about the past.

Finding parallel comparisons to the film is difficult. As a revenge thriller with lots of flashbacks it brings Steven Soderbergh’s “The Limey” to mind, while the deceptive technique of telling an entire story from one character’s point of view gives it a strong tinge of “The Usual Suspects.” Writing the script from a short story written by his brother, Nolan delves into all the conflicting emotions, judgments and instincts that comprise Leonard’s mind to show that the only reality we really have exists in our own mental constructions. “Sometime I forget that there’s a world outside of my head,” Leonard muses at one point.

Set in a Southern California wasteland of cheap motels and strip malls, the movie stars Guy Pearce who plays Leonard, an insurance claims investigator who was dealt a debilitating blow to the head as he defended his wife from an attack by two men. Leonard’s wound left him with a condition that prevents him from creating any new memories since the incident. Instead, he is forced to rely upon body tattoos, Polaroid snapshots and hastily written judgments and directions about whom he is and what he is trying to accomplish.

On his quest he meets Natalie (Carrie-Anne Moss), a bartender who professes to be his ally, and Teddy (Joe Pantoliano), a squirrelly man who claims to be a cop and also pledges his assistance. The plot switches tempo and focus many times, always leaving past assumptions overturned and forging new ones in their place. Like Leonard, we think we know what is going on, only to be proven wrong the following minute.

If there is one thing certain about “Memento,” it is that it signifies the emergence of Guy Pearce as a world-class actor. He showed great promise as Russell Crowe’s stoic alter ego Ed Exley in “L.A. Confidential” and as the bombastic prosecutor in “Rules of Engagement,” but Nolan’s film shows the young Australian’s talents in full bloom. Pearce convincingly exhibits the paranoia, contradictory impulses and illusions that make up his character, and he does this all without seeming overdramatic.

It demands a bit of patience at times, but the complexity and utter subjectivity of the movie make “Memento” one of those films that needs to be seen twice. The grace of the film lies in its refusal to be objective, to provide any clear-cut, definitive answers to Leonard’s situation. If “Memento” is effective in communicating a message, it is the moral ambiguity of us all and how hard it is to know what is real and what is not.