The first drafts of the script faced the challenge of updating the novel with contemporary technology, including cell phones, GPS, laptops, thermal imaging, and a post-9/11 world in New York City. In December 2007, David Koepp, who adapted the novel for Scott and Washington said: 'I wrote many drafts to try and put it in the present day and keep all the great execution that was there from the first one. It's thirty years later so you have to take certain things into account. Hopefully we came up with a clever way to move it to the present.' Koepp's drafts were meant to be "essentially familiar" to those who read the novel, preserving the "great hero vs. villain thing" of the original. Brian Helgeland, the only one receiving credit for the screenplay, took the script in a different direction, making the remake more like the 1974 film than the novel and, as Helgeland put it, making it about "two guys who weren't necessarily all that different from each other." Whereas the novel is told from more than 30 perspectives, keeping readers off balance because it is unknown which characters the writer might suddenly discard, the two films focus on the lead hijacker and the Metropolitan Transportation Authority employee with whom he communicates by phone. The new version sharpens that focus until it's almost exclusively a duel between disgraced MTA dispatcher Walter Garber and manic gunman Ryder.
In the book and original film, Ryder is "cold-blooded and calculating", but in the 2009 film he is a "loose cannon willing to kill innocents, not out of necessity, but out of spite." Also Ryder, in the original film and book, is portrayed as a normal looking businessman, while in the 2009 film he looks like he has adopted prison life, wearing very visible prison related tattoos and very laid back modern style of a biker. In the 1974 film, the main character is named Zachary Garber and is a lieutenant in the Transit Authority police; in the 2009 film, the main character is named Walter Garber and works as a subway train dispatcher. Ryder asks for $10 million dollars instead of the $1 million as in the original film and book and $5 million in the made-for TV movie. Ryder does not use the "Mr. Blue" nickname as the original film does; it is implied that Ryder is a nickname.