Mad Hatter is an alternative reality version of Nathan Johnson, created following the destruction of the Dark Portal and the formation of alternative realities. Mad Hatter came to co-exist in Nathan's main timeline.
Following the destruction of the Borealis, Nathan arrived back in City 14 to assist Holly Hills in investigating remaining members of the Clandestine Company whom were still trying to continue their experiments. Nathan ended up being incarcerated at an asylum, which was run by followers of the Company as well as head research Arne Magnusson. As punishment, Nathan was subjected to mind altering drugs which caused him to believe he was the Mad Hatter from Alice in Wonderland. His former girlfriend Olivia began working at the hospital, in which she broke Nathan out to help him. The pair of them moved to City 21, but unaware to Olivia Nathan's mind completely broke, forming a new, sadistic personality with it's own goals.
Nathan goes on a spree, kidnapping Diana Harris and murdering any witnesses or people trying to stop his brand new life.
His first murder victim Nick Munro returned to the death with the help of the Cult of Munro, who gave Nick strength and durability. Nick captured Nathan and brought him to the bridge where he originally died, intending to throw Nathan off the edge. After a brief disruption from Nick's son OJ, Nathan tackled Nick off the edge, although the pair survived, with Nick going into hiding. Nathan started questioning his own sanity when he came face-to-face with a lookalike of himself, and with books in the man's possession depicting Nathan's life over the past ten years. The man claimed that he was the writer of Nathan's life, and that the story is now complete. In rage, Nathan murdered the man and stole the book collection.
Nathan got arrested and charged with his crimes. Nearing the end of the road, Nathan pleaded that he was not guilty by reason of insanity. Using his remaining connections in higher places, he was packed off to an asylum located near Ravenholm, where he would reside until deemed fit to be released back into society.
Nathan was released from the asylum with the help of Frank Blackstone, who ordered him to unleash terror upon the new City 17 in order to cause a distraction.
- The character's behaviour and gimmick is based off that of Jervis Tetch/ The Mad Hatter from the DC Comics Batman franchise.