William Harris is a commander of the US Army. When the aliens attacked, he was tasked with keeping safe a team of scientists, who managed to save humanity. Since there was no safer place than the bunker they were holed into, the army allowed the commander and everyone else involved to take their families along, so William took his wife and three children with him.
At first, William struggles with both the death of his brother and the shame that he was ordered to lay back while his brother fought bravely. He even has nightmares of billy and his dead father saying that he is ashamed of him. This makes him take careless and dangerous decisions (like not wait until the leechers die) and he is also nearly killed once. When he realises they can't continue because it is too dangerous he breaks down and says he feels ashamed for not being as good as his brother. Christine then scolds him and brings him around, telling him that in order to lead them to safety successfully he must stop living in his father' s shadow. She tells him billy is a hero for stopping the spaceships, but if he dies or makes others die trying to prove himself, he will just be stupid. She adds that he can be a hero too, if he helps them all live and create a better world. William leaves and goes to sit alone, and Michael follows. He asks what's wrong insisting and says that whatever it is, he needs to keep it together because he is the only one who can keep the group safe. William then realises how much the group looks up to him and that in their eyes, he is already a hero. He then thanks Michael and goes back to christine. He kisses her and tells her they are staying as soon as they find a safe place. He then announces it and when they settle in he takes a bike and goes to see his father's gravestone. There he talks a little, saying that he wasn't a good father necause he made them both competitive and jealous of another, like he forced them both to follow in his footsteps. He says he is no more the man he used to be and is finally free from how his fathrr controlled his life.
When they create the camp and wait for the leechers to die out, they meet the most of the people they took with them. William notes that it is said that if you get lost, you should stay in one place to be found. They must have likelybeen in the same area with mre survivors before, but they didn't meet them because they moved all the time.
William is one of the very few members of the military left on the bunker, so his duties take too much time of his schedule and he doesn't see his family much. Christine argues with him all the time about tthis, but there is nothing that can be done. William is on lookout most of the time, and trains the relatives of the scientists who have offered to join them.
When they reach the military encampment they were before the invasion, William disagreed with the general there for many things, and both men took the situation to the edge, going as far as to make William impose a military dictatorship on the encampment. He seems to have regret his actions later though, as he questions whether this was a wise decision, and Christine supports him. After the military take over again, the group is exiled and William is spared for the sake of his brother.
Among the things William disagreed on, was the fact that the military would forcefully perform experiments on every survivor they would encounter, in hopes of finding a cure on the disease. In the first days of their arrival, all of them are suddenly taken into custody and have experiments made on them. They are however released after a couple of days, after which William clashes with the military harshly. While some of them realise what happened had to happen, everyone is angry at Mat still beig exerimented on. The general though said that Mat is unique and unlike anything they have ever seen, and they will not let him loose until all his secrets are revealed
During the takeover, he supports the man who is in charge of the operation, but the latter is killed and William is left to take charge. He then tells James he is clueless about what to do, but James says that the world doesn't always need a hero. He says that these are historical times, and if William succeeds, he will be the who did what he had to, if he fails, he will be the the villain of the story. Willi also says that the man he was a few years ago wouldn't eben dream of doing such a thing because of how his father taught him to follow orders blindly. Now he does what he does for his friends, family and the future of mankind in general so he doesn't care about these things.
After they are exiled from the military encampment, he and Michael have a talk, in which William admits that when he was promoted, he became a little thirsty for power and that played a role in the uprising. He wonders if things could have worked out had he not done that mistake, and apologises for not keeping them where safety is. Michael replied "If you had tried something different, we would still live under the rule of a man who was corrupted by power, and it would be his decision whether my son is a traitor to the aliens or not. I wouldn't have followed you then, and we wouldn't be friends now". William replied saying he just wonders if they could have kept the safety of the military base for all of them, and Michael said that they wouldn't be free then, and he never was a guy to forfeit his freedom over security. William asks if he thinks they are free now, running from flesh eating zombies and aliens, and Michael says "We walk the land of the damned. We are as free as it gets to be". William lets out a chuckle and pats him on the shoulder. He jokingly says Michael talks like his father, and thanks him.
After Steven's death, he is devastated and decides to step back and look after his family. Christine though is angry at him and breaks up with him for a while. William makes some bad decisions, and the group has a meeting without him, and decides that William has to stand back for the good of everyone. William confronts them and refuses to abandon authority. He questions everyone's ability to lead, and mocks Nichael saying "Are you going to lead them with all your "I wouldn't sacrifice reedom over security"crap? You would get everyone killed". Christine then intervenes too, and says William is no longer fot for leader, and should step back. William then pulls a gun on her, blaming her for taking his children away, and says he will take his children, leave and whoever wants to go with him can, except for those who questioned his leadership. Jason appears behind him holding a gun, but Michael decides to try and defuse the situation by talking to William. "Remember when I told you the "I wouldn't sacrifice my freedom for security crap?". Remember what you told me at that talk? You told me you thought it was your hunger for authority and power that drove us out of the encampment. That wasn't true then, but it is true now. Right now, you are tearing this group down. And we are all dead if you do. United is what's keeping us alive. Try to think about it logically, and tell me really if you are able to lead us. You know I'd follow you anywhere". William then lowers his gun, lets Christine go, and Jason lowers his gun slowly as well. William says leading them is all he has left, and taking that away from him will kill him. Michael comforts him, and Christine says he can focus on the children, as he is allowed to see them again if he wants to. A while later, William reapproaches his children, and although Brian has a hard time accepting him at first, he does later, although at some point he has an outbreak at him for killing Steven. William is later forgivan by all of his family, and accepted back. He and christine get back together again (Maybe christine gets pregnant at this point). After this, the family slowly heals, but William becomes overprotectiv of his remaining children afterwards (this leads to his corruption during the brian bullying)
When the Arian brotherhood leader is killed, he tells William he will someday be corrupted by the authority he is given, to which William replies he will not. This is forshadowing about when Brian is involved in the bullying of the child in the deadlands and William uses his power to cover the situation up, leading the people into a riot.
Sometime during the course of the series, William will have both of his hands broken as an act of subduction to another leader. This will scare the remaining group and cripple William, but in the end it will make them fight for their freedom
- He has very few myopia, for which he couldn't join the air force like his father and brother. he seemingly inherited this diseae from his mother
- While at first he shaves daily, later he stops as both he and Cristine like him having a small beard. This comes as a realisation that the laws and regulations that applied to the old world don't apply anymore