Shy, naïve Allison Perkins first appeared in Llanview in 1986 as an intern at Llanview Hospital. She took an interest in Dr. Larry Wolek's son Dan Wolek, who was an intern at the hospital. Though they went out on a couple of dates, nothing came of the relationship.

Allison soon fell under the spell of Mitch Laurence, who had been incarcerated at Statesville Prison - where Allison's father was the warden - for the murder of Harry O'Neill. Mitch pretended to have found God and was released from the prison, returning to Llanview as an evangelist preacher. Allison was one of many young women who fell under Mitch's spell, as he assembled his own commune at the Waterside Inn and coerced and drugged young women into being his disciples. Desperate to get even on Viki Buchanan for fingering him as Harry's killer, Mitch had Allison slip a drug into a pregnant Viki's drink when she visited the commune. Viki had an accident on the road and went into early labor, but the doctors managed to keep Viki from giving birth then. Mitch was supposedly murdered by Dorian Lord in the summer of 1986, but before he died he planted a post-hypnotic suggestion in Allison's brain, instructing her to steal Viki's baby and make it look as if Viki's alternate personality, Niki Smith, was the kidnapper. Allison dressed up as Niki, snuck into Llanfair and took baby Jessica to her mother's home in New Jersey. Maria Roberts (Cord Roberts' mother) found out about Allison and, wanting to get Clint for herself, manipulated the situation so that Clint suspected Viki had once again turned into Niki and kidnapped Jessica. Viki became angry that Clint suspected her, causing strife in their marriage. Satisfied with how much damage had been done to Viki and Clint's marriage, Maria later persuaded Allison to return the child to Llanfair. As Allison fled the scene, she was hit by a car. Left comatose for a number of years, she was never able to confess what she had done, or reveal Maria's part in the kidnapping.

Allison resurfaced in August 2001 at St. Ann's psychiatric facility, supposedly wanting forgiveness from Viki for the kidnapping all those years before. Very hesitantly, Viki agreed to visit Allison at St. Ann's and extended her forgiveness. Armed with Viki's forgiveness, Allison was granted release from St. Ann's, which was exactly what Allison wanted all along. Allison then shocked Viki and her family with the revelation that she had actually switched Jessica with another baby back in 1986. The baby Viki had given birth to was actually Natalie Balsom, who had been raised by Dr. Walter and Roxanne Balsom. Jessica, the baby Viki had raised as her own, was actually Roxanne's child, Allison claimed. Allison had tracked down Natalie hatched a plan to split her inheritance once her birthright was proven, but Natalie later rejected Allison and tried to forge a relationship with her new family.

Allison then launched another scheme by convincing Roxy to pretend she was suffering from hypoglycemia. They hoped to convince Jessica to pay for the expensive medical treatments, split the earnings and skip town. Jessica's boyfriend Seth Anderson learned about the scheme and alerted Jessica. To keep them from going to the police, Allison ran them off the road in her car, framed Roxy for the deed and then skipped town. When Allison read in the paper that Jessica was going to give Roxy $100,000, she headed back to Llanview with the intention of collecting her "rightful" share of the money. Allison admitted to Roxy that she had been the one to run down Jessica and Seth, not realizing that Roxy had been bugged by the police. Allison was arrested and sentenced to 20 years at Statesville prison in the summer of 2002.

While in prison, Allison became cellmates with Lindsay Rappaport. When Lindsay discovered that Allison's father was the former warden, and that she knew of a secret tunnel that led to the outside, she eventually persuaded Alison to break out with her. Allison soon kidnapped Roxy and Viki, who by this time had reverted to her alternate personality of Niki Smith. Leaving Roxy behind, Allison took Lindsay and Niki to the Buchanan lodge and was preparing to shoot one of them when the police stormed the cabin, along with Viki's husband Ben Davidson. During the rescue attempt, police officer Antonio Vega accidentally shot Ben, which sent him into an irreversible coma. Allison was sent back to St. Ann's.

In October 2002, a DNA test proved that Jessica was also Viki's daughter, meaning Viki actually had given birth to twins. Viki and Bo visited Allison at St. Ann's, desperate for answers. Allison told Viki to ask Mitch, signaling that Mitch was somehow involved in the events surrounding Natalie and Jessica's births. When reminded that Mitch was dead, Allison questioned whether that was true.

A very-much alive Mitch Laurence turned up in Llanview and, under the guise of Michael Lazarus, befriended Natalie. When Mitch and Viki came face to face, he revealed that he had drugged Viki and raped her around the same time she had conceived a child with Clint. Viki had become pregnant with fraternal twins: Natalie was fathered by Clint, while Jessica was fathered by Mitch. Viki's obstetrician, Dr. Walter Balsom, conspired with Mitch to keep the twin pregnancy from Viki and allowed Mitch to take his daughter as soon as she was born. Mitch, however, wanted his daughter to grow up in the lap of luxury and sent Allison to kidnap Clint's child and replace her with Jessica, leaving Natalie to be raised by the Balsoms. In early 2003, Mitch visited an insane and incoherent Allison at St. Ann's and told her to pull herself together, that there was much work left to do. Mitch subsequently was killed by Jessica, leaving it unclear what he had intended for Allison to do.

In January 2008, Jessica came face to face with Allison after a prank landed her in St. Ann's. Allison taunted Jessica, claiming to have a big secret about her family. Allison said she would reveal what she knew only if Jessica helped her break out of St. Ann's. Enlisting Natalie's help, Jessica smuggled Allison out of St. Ann's, with the intention of returning her there after learning Allison's secret. Allison demanded to be taken to the Lord family mausoleum, where she retrieved a package and gun that had been left for her by Mitch. Allison then eluded Jessica and Natalie and showed up at the Palace Hotel, where all of Llanview was attending an exclusive gala. Allison took Jessica at gunpoint to the roof of the hotel. Jared Banks attempted to free Jessica and, in a struggle for the gun, he and Allison fell over a balcony. Hanging on for their lives, Allison let go of Jared, saying her secret would die with her. Though she survived the fall, Allison was left in a coma. A DVD found in her possession was destroyed, leaving Jessica to wonder what secret Allison knew.

In February 2010, Allison Perkins resurfaced at Statesville Prison, visiting newly incarcerated Mitch Laurence while disguised as Roxanne Balsom. Allison told Mitch that Dorian's sister Melinda Cramer had died of natural causes, and then Mitch gave Allison a task to perform: take photos of all of his children and grandchildren. Allison complied, snapping photos of Shane, Bree and infant Sierra Rose. Mitch didn't understand why Allison took Sierra's picture, since it had already been revealed that Mitch's son Rex wasn't Sierra's father, but Allison said the baby would be his ticket out of prison. Allison then kidnapped the baby from Schuyler's apartment and then ordered Schuyler to help break Mitch out of prison in exchange for the baby. She revealed herself and the baby to Roxy at the hair salon. When Natalie arrived, Allison pulled a gun on her and then disappeared with Roxy and the baby while Natalie dealt with John McBain. Allison tied Roxy up at Kyle's apartment in the Angel Square Hotel, and then revealed to Roxy a secret involving her son that was so shocking, it rendered Roxy speechless. Allison received a call from Mitch and arrived at Statesville Prison with the baby and a gun, only to find that Schuyler had injected Mitch with a drug that would kill him if she didn't hand over Sierra. Inside the locked medical room, Allison then revealed that baby Sierra was actually Mitch's granddaughter because Schuyler was Mitch's son, not Rex!

Allison explained that the baby Roxy had delivered (Schuyler) was very ill when he was born so Allison switched the baby with a healthy newborn (Rex) who had been abandoned by his parents and brought to the hospital. Baby Schuyler made a full recovery but it was too late to reverse the switch, so Allison told her sister Leah that she had given birth to the baby but didn't want it and asked her sister to raise the baby. Schuyler refused to administer the antidote that would save Mitch, instead throwing it under the bed and walking out of the locked room with Sierra in his arms. Allison pleaded with the police to save Mitch, which they did, and then Mitch ordered Allison removed from his sight. Kelly and Todd then questioned Allison about Kelly's mother Melinda's death. Allison admitted that she planned to kill Melinda but claimed that Melinda was already dead when she arrived at the mental facility in California where Melinda was staying. When Roxy demanded to know where her infant son was buried, Allison stunned her with the news that her baby hadn't died at all and was actually Schuyler Joplin. After learning that Mitch and Roxy weren't his parents, Rex visited Allison at Statesville with Gigi to question her about his parents. Allison claimed not to know where Rex came from and denied Gigi's hypothesis that Allison was Rex's mother. When Rex questioned why Mitch's bone marrow was a match for Shane's even though he isn't related, Allison chalked it up to a coincidence. She told Rex and Gigi about the sample of Mitch's blood that Stacy had stolen and hid away at Rex's loft, and then she gave Rex and Gigi the name of a nurse who was working at the hospital when he was abandoned: Nurse Wojciehowicz, who just happened to still be working at Llanview Hospital.

On New Year's Eve 2011, Allison escaped from Statesville Prison along with nearly 200 other inmates and showed up at Llanfair, cornering Viki and Clint. Armed with a gun, Allison informed Viki and Clint that she no longer took orders from anyone and was taking advice from Oprah to empower herself. Allison claimed that she'd arranged the prison escape and complained that everyone else got credit for her work. Allison appeared ready to kill Viki and Clint but instead fired into a vase. Allison then began rambling on about the time she kidnapped Natalie at birth and replaced her with Jessica, and how she felt obligated to please Mitch and tell him what he wanted to hear even if it wasn't exactly true. As Viki and Clint struggled to understand what Allison was trying to say, Allison suddenly announced that Natalie and Jessica were both Clint's biological daughters. Allison said she felt forced to tell Mitch that he was father to one of Viki's unborn babies because it's what he wanted to hear and he would have killed her if he learned the truth. Allison said she faked the DNA test to show Mitch as Jessica's father. Allison said she tried to tell Jessica the truth several years earlier but Jessica refused to listen to her. Frustrated that Viki and Clint were skeptical about her story, Allison impulsively shot Viki. As Clint tended to Viki, Allison began chanting her name around the room and declared, "My aim is true!" before escaping.

Allison later resurfaced in an unknown location, holding a manuscript for a movie project called One Life to Live. She threw the pages at a person in the room, who turned out to be a bound and gagged Victor Lord, Jr. Victor escaped months later but was recaptured and held again by Allison. Meanwhile, Allison's brother Carl Peterson, with the help of Jeffrey King, orchestrated the public demise of Clint Buchanan by tampering with his medication. Once Clint was incapacitated, Allison arrived at the hospital and threatened him with a syringe.