Lone Wolf and Cub was created by writer Kazuo Koike and artist Goseki Kojima, who began publishing the manga series in Japan in 1970. The revenge story was epic in execution (it was close to 9,000 pages by the time it was done), acclaimed for its storytelling and its historical accuracy. It was influential in Japanese pop culture, spawning movies, a television series and even plays. The comics first began publishing in the U.S. in the late 1980s.

The story told of a shogun’s executioner named Itto Ogami, who starts on a path of revenge after his wife and the rest of his house is murdered, leaving only his infant son alive. Itto is joined on this quest by his son, Daigoro, who, as he grows up, is trained to be a fearsome warrior and joins him as a father-son team of assassins for hire as they travel the country and seek vengeance against the clan that killed their family.

The project has been at Paramount on-and-off since 2003 and at one point even had Darren Aronofsky attached to direct.

Walker rose to prominence in 1995 thanks to his script for David Fincher's acclaimed crime thriller Seven, which starred Brad Pitt and Morgan Freeman as two detectives hunting down a deranged killer who modeled his kills off of the seven deadly sins.

Walker went on to pen scripts for 8MM as well as Tim Burton's Sleepy Hollow, which starred Johnny Depp in the retelling of the American fable. He also penned 2010's remake of The Wolfman starring Benicio del Toro and Anthony Hopkins.

Walker's 2016 animated comedy Nerdland, starring Paul Rudd and Patton Oswalt, drew upon his early days in Hollywood trying to make it as a screenwriter.

He is repped by Brillstein Entertainment Partners and Ziffren Brittenham.