Mary Young an idealistic doctor who wants to help people has selected Evil Ernie as a subject to test new invention Neurotech. She truly believes that this machine is able to remove killing urges from people. She signs a contract presented by Commissioner Stone, without reading the fine print, and is given the rights to cure Ernie.
The Night the curing takes place, Ernie dies. Mary is shaken by the result and goes home, where her family and Neurotech people had prepared a success party. Mary calls back to the Clearview mental Institute to check on Evil Ernie's caretaker, who too was shaken by his death. But Ernie answers the phone and says that the caretaker is dead. Mary thinking it's a crude joke, decides to return to asylum. On the way there she is run off the road by Evil Ernie. When she gets there all the staff are dead. She finds Leonard Price in one of the cells and releases him. Dr. Price had prepared for Ernie's escape and arms himself. Mary protests, and says that she is no vigilante. In the end she too takes a pistol and joins Price in the hunt.
Mary and Price see some ghouls on the way and Price sees it as opportunity to teach Mary to take care of herself. Mary fires her first gun that day, and kills some ghouls. Then their hunts leads to Evil Ernie, they try to take him out, but are overpowered. Then they devise a plan how to stop Ernie, a shot to the head. They catch up with Evil second time in a police station, there Mary gets a chance and shot Ernie, he did feel pain but, it wasn't enough, he and his ghouls were still coming. Ernie nailed Mary to the ground with knives through her clothes, and planed to attack her family. Mary managed to get free and met up with Leonard, who had found a rocket launcher, the hunt for Ernie continued. Mary and Price made it to her house before Ernie had a chance of killing anyone. Again, Mary is the one who fires the last shot to Ernie with a rocket launcher, killing him and saving the day. Not able to forget what they saw, Young family took survival courses, to prepare themselves for the worst.
Months later Mary Young is accused for creating the Psycho Plague, although Commissioner Stone was the one giving ordered and built the machine, he almost got away from the charges by pointing out that fine print Mary didn't read. People wanted to see someone take the fall for creating the plague, and all the fingers were pointed to Mary. On one of the hearings Commissioner Stone started to freak out and occasionally spoke like Evil Ernie.
Mary got the idea that Ernie wanted to surface again, and then Price walked into the courtroom and shot Stone. Mary wanted to warn Price not to do it, but was too late. Stone dead Ernie had a way to come back from the dead. Mary and her sister Judy Young utilize their training and try to take out Ernie there, but like before just bullets won't do a thing. They then retreat, and escape the courthouse. Watching how Ernie leaves, they double back to check on their brother Rick Young, who got mortally wounded.
Just when they are about to shoot the corps in the head to prevent him to rise again, military police arrives and arrests Mary, leaving Judy and Billy Young behind. The man who ordered the arrest was General Ramsey, he wanted Mary and Price to be his consultants. When they are in the cell, and Ramsey refuses to release them; Mary knocks him out and unlocks the door. Mary and Price follow Ernie to the white house but fail to save the president. They survive thanks to Ramsey, only to be locked up by him again. Ramsey don't run the operation that long, after failing his mission he is demoted; Mary and Price are released and given the command over his troops. Mary wants to do things more humane way, but Price takes the order "any means necessary" and works on that principle. They return to old asylum and retrieve the Neurotech machine. Mary prepares herself to enter the mind of Evil Ernie when he is captured by Price's brute force. She appears in Endless Graveyard, still thinking that she's in Ernie's mind, but she in fact was in hell. She moved towards Lady Death's castle, thinking that when she kills her, Evil Ernie will be cured. She is attacked by Purgatori, who doesn't want anyone to ruin her chances to take on Lady Death herself. Purgatori is about to kill Mary, when her connection to hell realm is severed and she disappears. Back in real world, Mary falls into a coma.
When Mary wakes up, she wants to get away from the killing and starts working as a volunteer in a hospital. Military still holds her responsible for the Psycho Plague. One day returning home from work, he gets a visit from Evil Ernie. Ernie blackmails Mary to work for him, with the threat to kill her brother Billy. Evil wants Mary and other scientists to bring Lady Death to earth. The work took several months but finally they succeeded. But the story doesn't get a happy ending, when Lady Death came to earth a wave of arcane energy was released, and it was tearing earth apart. Lady Death not wanting to destroy earth, asked herself to be sent back. Done her work, Evil Ernie kept his word and released both Mary and Billy.
They then headed back toward Washington to find their sister Judy. They almost got killed by Price's newest creation Crippler on their way there, but manage to get away with their lives. Mary and Billy follow Judy's tracks and meet with people who she's saved. Eventually they are able to find her, but then Billy got careless and gets shot. Knowing that Evil Ernie goes for nuclear arsenal, sisters are separated again. Judy follows Ernie and Mary takes care of Billy. Finding the first medical center, Mary forces doctors to save Billy first. However main doctor just then had a heart attack, and second best doctor was drunk; Mary was forced to operate on Bill herself. In the end Mary wasn't able to save Billy, he dies on the table. Mary takes him to the woods to make sure he won't rise like Rick did, but can't do it, being up for several days, she falls asleep. When she is awakened by her sister, who had returned, Billy has gotten better somehow and lived again. Picking up Evil's track they hunt him for a while, but when Purgatori uses her blood-link with Mary to transport herself near Ernie and kidnap Chastity, the Youngs stop the hunt and take care of Mary.
Time has passed Mary has lost sight of her sister Judy, Billy has suffered a stroke that took him closer to death, he now hears the dead. Mary watches out for Billy and tries to survive on the east-side of the wall. Things turn to worse, Mary is kidnapped by the dead, and Billy is left behind alone. The dead want to judge Mary for killing countless number of dead ones. Rick Young intervenes and says that Mary is one of the originators, if wasn't for her, there would be no dead ones. Rick manages to convince the dead to let Mary live. Mary joins forces with Judy's old partner Sam Gunhill and they locate living Ernest, they convince him to join them in stopping Evil Ernie. Mary makes it to Norad just as Rick and Dr. Price are attacking the facility. All the players are moving in to stop Ernie. Mary is attacked by her now dead brother Billy, and she is again saved by Rick. Mary witnesses the final battle between Price and Evil, knowing that Price is too far gone, she sets the nuke and escapes with her brothers.
World ends few days later, but Mary is created anew, she appears on the dead planet as does her brothers Billy and Rick. She joined the community were dead and living lived in harmony. She led protests and marches, the dead tried to kill her several times, but failed. In the end it was radiation poisoning that killed her. After her death she was seen as a savior, and was worshiped.
Mary Young is a budding psychiatric specialist who is in the market for study of the minds "Moralistic Compound", the cognitive prerogative of why some people lack a certain moralistic code. In laymen's terms; why it is that some people are or happen to be inclined towards evil. About five years ago Ms. Young made a regular visit to Widmark Prison before it was bombed through presidential order, in order to check up on the black sheep of her family, Rick Young. She still loved her brother and inquiried why Rick did what he did to end up a prisoner there, only to receive a rather somber answer in the process. Jumping ahead about half a decade Mary is next seen infiltrating the government quarantined zone of what used to be Clearview Mental Institution, searching for clues as to the odd occurrences that happened there akin to when and how Widmark prison went up like a fire cracker were her brother had died during the bombing. After spying a rather iconic hallmark from afar however the good shrink is caught then caged by the hazmat team patrolling the area. When a mysterious voice emanates from some random container, Mary lends her ear only to find herself repulsed by the escape plan it cooks up. Around that time Ernie, Who'ed been recently sent back to earth by Lucifer, dispatches the guards and makes his way towards her confines in order to retrieve his partner Smiley; who incidentally was her unknowable cellmate who'd she had been talking to. On his suggestion Ernest also frees a reluctant Mary and brings her along on his new quest.