When genius Los Angeles-based computer scientist Hannon Fuller (Shine's Armin Mueller-Stahl) is murdered, police detective Larry McBain (24's Dennis Haysbert) suspects Fuller's long-time partner and successor in the firm, Douglas Hall (Boston Legal's Craig Bierko).
However, the transition of power is further confused by the sudden appearance of Fuller's previously unknown daughter, Jane (Boardwalk Empire and Perry Mason's Gretchen Mol).
On the thirteenth floor of his corporate tower, Fuller had been working on a highly secretive project, creating a virtual reality simulation of 1937 Los Angeles.
Somehow, Fuller had become aware that someone was after him.
Without telling his assistant Whitney (Daredevil's Vincent D'Onofrio), Fuller left a message for Hall in the simulation, but Hall - when he finally "jacks in" for the first time - is unable to find it.
Parallel to the murder investigation in 'modern day' Los Angeles, Hall has to navigate the 1930's simulation to try and recover his mentor's all-important message.
While the late 1990's ideas of "sci-fi" technology in The Thirteenth Floor already look horribly dated to modern eyes, the story itself is incredibly smart and engaging.
While it's a film I was passingly aware of, it wasn't until its praises were sung so highly in the simulation hypothesis documentary A Glitch In The Matrix (which, I have to confess, has really got under my skin of late), that I thought I'd better check it out.
Acquired for a couple of quid on eBay, The Thirteenth Floor has elements of The Matrix, Westworld, Dark City, The Truman Show and probably several other reality-challenging stories that I can't put my finger on right now.
It's very much a mystery, rather than an action movie, with the observant viewer twigging what's really going on just minutes before the protagonist does.
Even the aspects that, initially, come across as a tad clumsy - such as the romantic sub-plot - are eventually explained in the superb script from Daniel F. Galouye Ravel Centeno-Rodriguez, and director Josef Rusnak.
And I really get why the "simulation theorists" in the documentary rate this 100-minute movie, as its approach to the core theme, while superficially simplistic, is actually quite textured and fascinating.
While I'm usually an advocate for leaving old properties alone, I reckon The Thirteenth Floor is due a 21st Century remake - in the style of the HBO's Westworld reimagining of the original 1970's Westworld films and TV series.