Walter goes on a shooting spree, killing hosts that had shot him in past storylines. Being a host, he shouldn't have remembered being harmed from past story lines, due to his re-programming, and it is thought that this glitch was due to a software update. Conspicuously, he leaves three hosts unharmed, none of which had ever harmed him. 
After Old Walter went off his loop and killed six hosts that he was never scripted to kill, he carried on a conversation, seemingly with nobody, in which he exclaimed, "I need more milk, Arnold!"
The New Walter is shown in Sweetwater with Rebus and a blond guest with long hair. Rebus taunts Dolores with comments about her vagina and private parts. He insinuates that he and the other two will 'have their way' with Dolores sexually.
Dolores returns home to her ranch alone. As usual, Rebus and company have killed her father, Peter Abernathy. At first Dolores sees the Abernathy who used to be the Mariposa bartender. Then, she remembers a time when her previous father was still active and had not been decommissioned. It is evident that during this time, she has memories of times when Rebus and Old Walter would come to the ranch and kill her father, because not only is the previous Peter Abernathy present, but Old Walter is present as well.
Shortly after the Gala Massacre, Walter is with Rebus as several Hosts playing a game of "William Tell" with a captured guest. Walter misses his shot, and claims the woman wiggled. Rebus tells him that he will never survive the journey and then kills the woman. Walter follows Rebus in search of more targets.
Old Walter was unstable, and that is why he was lobotomized and decommissioned. He spoke to Arnold (who has been dead for over 34 years), and he seemed obsessed with milk when he was speaking with Arnold.
Both Walters are psychopaths who take joy in killing Dolores' parents, and raping her mother. Walter has even been known to rape Dolores' mother after she was "dead".
Walter plays the role of sidekick and Rebus is the leader of the two of them. Walter usually gets killed in his story line. Sometimes he is killed by Rebus.
- Season One
- Season Two
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