Nicole Wallace was a serial killer and criminal mastermind whose crimes were often investigated by Robert Goren and Alexandra Eames. Though accused of murdering several individuals, she was only arrested once and was found not guilty at the resulting trial.
A brilliant, calculating sociopath, Nicole was the only person who was ever able to get the better of Goren and took particular delight in confronting him about his unhappy childhood and career hurdles, which he always retorted by regularly regarding her own traumatic past and failures at a safe, normal life.
Very little is known about Nicole's past, although it was apparently so painful that she went to great lengths to keep anyone from learning about it. As best as can be determined, she was born somewhere in Queensland, Australia. Detective Goren once speculated that she was molested by her father from the age of three. Nicole has vehemently denied this is true, but once said in private to Gwen Chapel that "sometimes daddies love too much."
Nicole later surfaced in Thailand, where she met a charismatic sociopath named Bernard Fremont. Fremont saw great potential in her and trained her as his apprentice-in-crime. Together, they robbed and murdered eight tourists, for which she was imprisoned for ten years. While in prison, she learned to speak Thai, though only low-class, likely picking up the language from her fellow prisoners. After she served her time, she moved back to Australia to start a new life. In 1995, she was living in Bendigo and was vaccinated for anthrax there. One year later, she met a man named Daniel Croydon, who was studying anthrax in Bendigo.
As an adult, she married Rohan Bartlett, and the two had a daughter named Hannah together in 1997. Things were apparently normal up until her daughter Hannah turned three. After that point, Nicole began to fear that her daughter Hannah would become a rival for Rohan's affections; Goren later speculates that she had internalized her father's excuse that young girls are too attractive for men to resist. On September 12, 2000, while visiting Stradbroke Island at the beach with her daughter, she broke the girl's neck and arm, killing her, leaving her feeling remorse with what she had done. The child's father reported the crime to the Queensland Police at 2:30pm. Then, she later came up with the cover story that her daughter drowned in the waters off Stradbroke Island. She was never conclusively connected to the crime, but a year later, she left the country under the name of Elizabeth Hitchens after her daughter Hannah's body was discovered. Police in Brisbane would later find the body of an unidentified woman, suspected to be the real Hitchens.
Nicole first became known to Goren and Eames while using her Hitchens identity. Under this alias, she was employed as a visiting professor at Hudson University. While there, she became romantically involved with Professor Christine Fellowes, who was in line to become the head of the American Studies department. Wallace arranged for the dean's murder, knowing he was deciding on that position. Nicole hoped that Fellowes would get the position because of the suspicion cast on another candidate through the killer, Mark Bayley. To cover her tracks, she poisons Bayley after talking with Goren. However, her scheme is eventually discovered, and her fake identity's embezzlement is exposed, which gives her motive for the murders. As a murder suspect, Nicole could be deported back to Australia because she lacks American citizenship. When Eames and Goren arrived to arrest her, she had already fled. (CI: "Anti-Thesis")
She eventually meets a man named Gavin Haynes while on the run, seducing and marrying him. Nicole is thus safe from extradition since she becomes an American citizen upon her marriage. She decides to get revenge on Goren for exposing her scheme. To this end, she seduces and sleeps with Doctors Roger Stern and Scott Borman, also stealing two grams of anthrax from Davis' personal collection. She then met a woman named Connie Matson at a bar near a U.S. Air Force base and slept with her to gain her trust. Nicole then persuaded Connie to get some anthrax vaccine boosters so she could buy them from her. (CI: "Zoonotic")
When Connie managed to get the vaccines, Nicole killed her by hitting her over the head with a dumbbell, stole the vaccines, and framed Dan Croydon, a deadbeat dad whom Nicole knew would remind Goren of his own father. When Goren relentlessly pursued Croydon, she invited herself into Croydon's apartment, had sex with him, and enticed him to write a note expressing his anger at Goren. When he was finished, she killed him and made it look like a suicide. She then left the vaccines and vial of anthrax on a train to Montreal to prove Croydon's innocence and ruin Goren's reputation. Nicole later met Goren in a diner and taunted him. She also introduced him to Gavin. Goren had her arrested on suspicion of stealing the anthrax and tricked her into revealing her true identity. She is then arrested for murder. (CI: "A Person of Interest")
The marriage ended after Nicole said that she was unable to bear children and "didn't see the point" of seeing a doctor about it. Sometime after, Nicole took a new lover, Ella Miyazaki, and began training her to be her accomplice, just as Fremont had trained her. Upon learning that Haynes had revealed her infertility to Goren and Eames, she sent Ella to kill her ex-husband by trapping him in an elevator and stealing his asthma inhaler so he would have an attack and suffocate. However, this attempt was averted by Goren. Eventually, the murder of her own daughter Hannah was revealed, which persuaded Ella to turn on Nicole. When Nicole figured it out, Nicole killed her and she faked her own death. (CI: "Great Barrier")
Nicole re-emerged a year later, now working as a librarian and engaged to Dr. Evan Chapel; however, it is strongly implied that she murdered Evan's brother Larry and made it look like an accidental drug overdose. Goren believed that Nicole was planning to kill Evan's daughter Gwen in order to collect on the girl's trust fund. During the investigation, Goren learned that Evan was, in fact, trying to kill Gwen, and Nicole was trying to protect the girl, whom she had grown to love Goren confronted Wallace and told her that she would always pose a threat to anyone who got close to her, and implored her to help him protect Gwen. Nicole gave Goren evidence implicating Chapel in the murder of his wife and the assault of his daughter but insisted that she could be a good mother to Gwen. She then kidnapped the girl, but, in a rare moment of conscience, left her with her aunt in Arizona. She then left a voicemail for Goren admitting that he was right and cursing him for taking away her last chance at happiness. (CI: "Grow")
In 2005, Bernard Fremont was arrested for the murder of Russ Corbett. As he was leaving the courthouse after his arraignment, an unidentified woman stabbed him with a syringe, killing him instantly. Though he would never be able to prove it, Goren believed Nicole to be the assailant. (CI: "Slither")
In 2008, she was murdered herself by Dr. Declan Gage, who cut her heart out after manipulating her to murder Frank Goren, Robert's brother. According to Gage, her last words were "Tell Bobby he was the only man I ever loved." While it's never revealed who Bobby was, it's possible she means Goren since his first name is Robert (CI: "Frame").
- Dr. Scott Borman and Roger Stern
- Victim: Officer William Davis
- Larry Chapel and Evan Chapel
- Victim: Monica Chapel
- Attempted Victim: Gwen Chapel
- Unknown dates from 1985 to 1987, Thailand: Eight unnamed men (all seduced by Nicole and killed by Fremont)
- September 12, 2000: Hannah June Bartlett (twisted her arm until it fractured and broke her neck)
- Unknown date in 2001: Elizabeth Hitchens (murdered)
- New York City, New York:
- September 25:
- Franklin Winthrop (bludgeoned with a gavel by Bayley at Nicole's direction)
- Kate Robbins (bludgeoned with a gavel by Bayley at Nicole's direction)
- October 2: Mark Bayley (poisoned with peanut oil in his nicotine gum)
- September 25:
- April 17: Connie Matson (bludgeoned over the head with a dumbbell)
- April 23: Daniel Croydon (strangled and staged his death to look like a suicide)
- August 2005: Larry Chapel (injected with a fatal dose of potassium chloride under his tongue)
- December 2006: Bernard Fremont (poisoned)
- August 2008:
- Her fingerprints are later matched to a murderer named Madeline Haynes on the French crime series Jo and according to actress Olivia d'Abo and the series creator René Balcer, Madeline is Nicole Wallace with a new alias. Peculiarly, her DNA wasn't a match, meaning she likely used forensic trickery to escape and assume a new identity.
- Viewers were polled to see whether Nicole would die on Great Barrier. East Coast viewers saw Nicole live; the West Coast viewers saw her die.