Snow Crash is the story of samurai programmer Hiro Protagonist and of youthful skateboard courier Y. T. The two live in a dystopian hyper-corporate future with a rich but commercial simulated online world underlying most of society. Partnering to go into the intelligence business, Hiro and Y. T. run afoul of a scheme to use mind control to reshape society through applications of an ancient language that speaks directly to the human brainstem.
Hiro Protagonist is a hacker and pizza delivery driver for the mafia. He meets Y.T. (short for Yours Truly), a young skateboard Kourier (courier), during a failed attempt to make a delivery on time. Y.T. completes the delivery on his behalf and they strike up a partnership, gathering intel selling it to the CIC, the for-profit organization that evolved from the CIA's merger with the Library of Congress. Within the Metaverse, Hiro is offered a datafile named Snow Crash by a man named Raven who hints that it is a form of narcotic. Hiro's friend and fellow hacker Da5id views a bitmap image contained in the file which causes his computer to crash and Da5id to suffer brain damage in the real world. Hiro meets his ex-girlfriend Juanita Marquez, who gives him a database containing a large amount of research, positing connections between the Snow Crash virus, ancient Sumarian culture and the legend of Tower of Babel. Juanita advises him to be careful and disappears.
The Mafia boss Uncle Enzo begins to take an paternal interest in Y.T. Impressed by her attitude and initiative, he arranges to meet her and offers her freelance jobs. Hiro's investigations and Y.T.'s intelligence gathering begin to coincide, with links between the neuro-linguistic viruses, a religious organization known as Reverend Wayne's Pearly Gates and a media magnate named L. Bob Rife beginning to emerge. Juanita's research showed that the ancient Sumarian ur-language allowed brain function to be 'programmed' using audio stimuli in conjunction with a DNA altering virus. Sumarian culture was organized around these programs (known as me ) which were administered by priests to the populace. Enki, a figure of legend, developed a counter-virus (known as the nam-shub of Enki ) which when delivered stopped the Sumarian language from being processed by the brain and led to the development of other, less literal languages, giving birth to the Babel myth. L. Bob Rife had been collecting Sumarian artifacts and developed the drug Snow Crash in order to make the public vulnerable to new forms of me which he would control. The physical form of the virus is distributed in the form of an addictive drug and within Reverend Wayne's church via infected blood. There is also a digital version to which hackers are especially vulnerable as they are accustomed to processing information in binary form.
Hiro heads north to where the Raft, a huge collection of boats containing Eurasian refugees, is approaching the American coast. Rife has been using the Raft as a mechanism to indoctrinate and infect thousands with the virus and so import it to America. Y.T. is captured and brought to Rife on the Raft, who intends to use her as a hostage, knowing her connection to Uncle Enzo. With help from the Mafia, Hiro makes it onto the raft and recovers the nam-sub of Enki which Rife had been concealing. With help from Juanita who had previously infiltrated the Raft, the nam-shub is read out and Rife's control over the Raft is broken. Rife flees the Raft, taking Y.T., and Raven attempts to activate the digital form of Snow Crash at a virtual concert within the Metaverse. Hiro is able to neutralize the virus and Y.T. escapes. After a confrontation with the Mafia, Raven is injured, and Rife is killed as he attempts to flee on his private jet. Y.T. is reunited with her mother and Hiro and Juanita appear reconciled.