Mickey and Lou are twin sisters who are the leaders of a nationwide gang of marauders known as the Highwaymen, who pillage, enslave, or kill anything in their path. They murdered their father for the position of leader of the group. Lou acts as the muscle while Mickey acts as the brains; despite their differences they are a force not to be trifled with. Currently, it is known that her father used to be the leader but after he became a problem, the twins murdered him and they both took up the role as leader.
Mickey and Lou led a charter of Highwaymen to conquer Hope County. When they heard Hope County's Scavengers recruited Thomas Rush's group to overthrow the Highwaymen, Mickey and Lou orchestrated an ambush on Rush's train. As the Highwaymen pillaged Rush's train, the twins told Rush's group that everything they own is now theirs and they will personally hunt them all down like "rabbits". The twins chased Rush, Garrett Barnes, and The Security Captain to the ledge of a cliff and cornered them.The twins told the group that their father told them that there are two types of people in the world: problem solvers and problem makers. With that in mind, the twins told them they are looking for problem solvers to serve their interests and will reward them if they are useful. If they are problem makers, then the twins assured them that they will "solve" them. Barnes tries to ingratiate himself to them by revealing his group's contributions to rebuilding America and Rush's useful expertise. After Rush refuses to side with the twins, Lou brutally executed Barnes with her custom helmet. After seeing that Rush would be uncooperative, the twins were about to kidnap Rush and the Captain until Rush tried to knock down some of the Highwaymen as a distraction and pushed the Captain off the cliff so they may escape capture.
Ever since the Captain escaped capture, the Captain has rallied Hope County's Scavengers to become an effective resistance force against the Highwaymen. The twins will comment on the Captain's progress of building up their forces as they recruit Guns for Hire and specific specialists the twins captured. Eventually the twins became frustrated with the Captain's insurgency and decided to make a show of force. The twins kidnapped several of Prosperity's children and held them hostage. Afterwards, they made a ruckus to lure the Captain and Carmina Rye to their location. Mickey scolded the Captain for taking from them and throwing everything out of balance. When Lou suggested they just kill the Captain, Mickey refused as she didn't want to create a martyr. Mickey told the Captain that she wants all their followers to understand that their help is a curse, and promised to take everything the Scavengers build; and when they have nothing left, the twins will end them. While Lou gives one of the children a pin removed hand grenade and tells him to not drop it, Mickey tells the Captain that they will take everything they hold dear for making them look weak, starting with Prosperity. Lou adds that what they can't take, they'll break. After Mickey throws the grenade safety pin at the Captain, she threatens them that they better be gone when they come back. The twins eventually ordered a full scale assault on Prosperity but the Captain and the Scavengers managed to fend off the attack. The Scavengers sustained heavy casualties during the defense of their home however, giving the twins an advantage in the war.
The Captain however went on to make an alliance with the New Eden cult, forcing the Highwaymen to fight the war on two fronts. The twins retaliated by recapturing Rush and several Scavengers and are holding them hostage at the old fertilizer plant. The twins rigged timed explosives to take out the trapped hostages, forcing the Captain to race against the clock to rescue them all. The twins kept Rush inside the plant and ordered the Captain to meet them there unarmed. Once inside the plant, the twins attempt to coerce the Captain to handcuff themselves(they can either give in or resist, either way they end up handcuffed, except that if they refuse, Lou handcuffs the Captain by force), so they can watch as Lou shoots Rush in the head with a shotgun. As the twins beat on the Captain and tried to demoralize them, the Captain broke out of their handcuffs in a rage and began to power through the twins. Mickey managed to shoot the Captain out the window to subdue them.
During the game's second intermission, a flashback shows that when the twins were kids, the twins' father -- Vince—took them away from their mother. In their final moments together, the twins' mother warned Mickey that they need to look out for one another because their father won't. Their mother accused Vince of creating more problems for the world, leaving a lot of dead bodies and not caring who he hurts. After witnessing the Captain "hulk out", the twins became concerned about the Captain's newfound strength; and Mickey surmised that it might have something to do with the Captain's trip to New Eden and suggested they pay the cult a visit.
During the mission Inside Job, the Captain infiltrates the Highwaymen's prison and overhears the twins talk about the New Edeners they interrogated. Mickey told Lou that they wouldn't be able to garner any information from them if she kept cutting out their tongues, but Lou seems unconcerned about her methods. Mickey stressed to her sister that they need to ask more questions in their interrogations and suggested that she handle the New Edeners, but Lou firmly stated she knows what she's doing. A Highwayman interrupted their dispute to inform them that someone important wanted to talk to them.
The Captain later sees the twins again after winning the Highwaymen's Demolition Derby. After winning the derby as a disguised Highwayman participant, the Captain was rewarded with an invitation to the annual dinner for the charter Highwaymen leaders that is hosted by the twins. When the Captain arrives at the dinner, Lou seemed to recognize the Captain, only for her to declare she only knew them as the derby winner and didn't in fact see through the Captain's disguise. Lou and the other Highwaymen leaders are impressed by the Captain's performance at the derby and praised their capabilities. During the dinner, Mickey arrives and revealed the important person they've been negotiating with was Ethan Seed, who promised to provide the twins New Eden's sacred fruit, which is said to grant those that consume it superhuman strength. Mickey reveals that they plan to share the fruit with the Highwaymen leaders that pay the "right price" for it. The Highwaymen leaders are skeptical of the fruit's properties however, and when one accused the twins of "going soft in the head" like their father, Lou breaks a plate and stabs him to death with one of the shards. Ethan stipulated that he will only give the twins the sacred fruit if they burn New Eden to the ground and demands they do so immediately; to which the twins begrudgingly agree to his terms. Ethan went on to open the gates of the New Eden compound for the twins, who proceeded to destroy the compound and kill many of its inhabitants. The twins were met by the Captain however, who defeated them in battle. As the twins began to bleed out on the ground, Mickey revealed she regretted breaking her promise to their mother that they not end up like their father. Lou tells her they had a lot of fun though, which resulted in the sisters laughing about their anarchic lives. Lou however, succumbed to her wounds and passed away soon afterwards.
Lou is described as impulsive and unpredictable. She seems to have no concept of long-term planning. For example, Lou pulls a pin out of a grenade and suggests killing a group of Prosperity children, disregarding the fact that everyone would have been killed, herself included. Later in the game, Lou tries to extract information from a group of convicts by cutting their tongues out. When Mickey exasperatingly points out that the "rabbits" can't talk without tongues, Lou just laughs it off.
Lou is also depicted as being far more violent than her sister, oftentimes for no reason. During the live action trailer The Stronghold Must Fall, Lou is seen smiling before she brutalizes a bar patron with her motorcycle helmet simply for speaking to her. (As a result, the Twins kill every person in the bar.) Even while dying, Lou is unrepenant of the chaos and brutality she has helped to spread, merely commenting about the fun she'd had during her short life.
- Lou and Mickey like to call the people they prey upon "rabbits"(in reference to how actual rabbits have a tendency to flee from their prey).
- Lou along with Mickey, are the youngest main antagonists in the franchise. Yet it's possible that Batari and Ull are around the same age or bit older.
- Lou can be compared a bit to John Seed (If you do not count the religious part of John), as she's the most sadistic and unpredictable of the sisters.
- Along with his sister Mickey are the third antagonists who are kingpins, the first is Hoyt Volker.
- Pagan Min is also a kingpin, but his main role is that of a dictator.