On the evening of October 29, 1984, Nancy entered her room to discover Mike stealing money from her piggy bank. She tried to stop him, but he managed to outrun her. While in the school parking lot the following morning, Nancy was looking over Steve's college essay when they witnessed Billy Hargrove and Max Mayfield arrive. Later that day, after receiving a flyer for Tina's Halloween party, she tried to convince Jonathan to attend. However, he refused. That night, Nancy and Steve had dinner with Mrs. and Mr. Holland. When Nancy inquired about the 'For Sale' sign in their yard, they revealed they had hired Murray Bauman, a private investigator, to investigate Barb's "disappearance". Overcome with grief, Nancy excused herself to the bathroom, where she began crying over the loss of her friend. The next day, as Nancy and Steve were studying in the school library, she noticed a person who resembled Barb, reigniting her grief. She then told Steve that they should tell Barb’s parent’s the truth about her death. After reminding her that it would be too dangerous to do so, Steve managed to convince Nancy not to say anything and to go to that night’s Halloween party so that they could have a normal night. That night at the party, Nancy became intoxicated. Steve tried to get her to stop drinking, accidently spilling Nancy’s drink on her costume. While attempting to clean herself, Nancy revealed to Steve that she did not really have feelings for him. Upset, Steve left the party. Nancy was later taken home by Jonathan. At school the next day, Nancy tried talking to Steve, wanting to know why she had not seen him that morning. Steve recounted the events of the party to her. Nancy tried to assure Steve that what she said wasn’t true, but when she didn’t tell him that she loved upon his request, he left. During lunch, Nancy spoke with Jonathan for confirmation of the party’s events. She then confided in Jonathan, telling him how she’s had to pretend everything was ok and tired of how the people at the lab have gotten away with what they have done. Nancy then got an idea on a way to possibly expose the lab. They both skipped fourth period, going to RadioShack to buy a Walkman. After school, Nancy called Mrs. Holland, telling her that she hasn’t been honest about Barb and to meet her at Forest Hills Park the next morning.

As Nancy and Jonathan waited in the park, they had a suspicion of being watched, prompting them to leave. After getting inside the car, they were then approached by agents who has been disguised as regular people. After being taken to the lab, Nancy and Jonathan were locked in an interrogation room. Eventually, Owens appeared and began giving them a tour of the lab, all the while explaining how the lab is trying to fix their “mistakes”, admitting culpability to Barb’s death in the process. After being warned not to say anything, they were allowed to leave. Once in the car, Nancy revealed the Walkman, having recorded everything that Owens had said. Nancy and Jonathan then traveled in the direction of Bauman's location, spending the night in a motel. While there, they showed each other their matching scars, reminiscing about their previous adventure. Nancy asked what happened between them, saying that she waited for Jonathan before ultimately ending up with Steve again. Jonathan retorted by saying she only waited a month and he was busy looking after Will. No more was said and the two went to sleep. When they arrived at Bauman’s residence, they presented the recording of Owens. Bauman claimed it wouldn’t be enough evidence to shutdown the lab, as it could easily be destroyed and the details of the story would be too extraordinary for the public to accept. He then proposed to Nancy and Jonathan that they “water down” their story in order to make it more appealing to the public. After altering their story to say that Barb died from a chemical leak originating from the lab, they placed the evidence in several envelopes to be sent to the Chicago Sun-Times. Murray offered Jonathan and Nancy his guest room, presuming the two were a couple. When they denied this, he easily deduced that there was sexual tension between them. Murray bid them goodnight and left them restless over his statements of their issues withholding them from getting together. Eventually, Nancy and Jonathan gave in and kissed one another before sleeping together in the guest room. The morning after, Murray cooked them breakfast, satisfied that his deductions were true. As they were saying goodbye to Murray, he told them to never return or contact him again. Upon arriving back in Hawkins, they realized something was wrong upon seeing the Byers' household strewn with Will's drawings of the underground tunnel system. They traveled to Hawkins Lab where they were soon met by Steve, Dustin, Lucas, and Max emerging from the woods after hearing noises from the lab.

Nancy also found that the power was turned off because there were no lights turned on and the gate to the lab was not opening. When the power was restored and the gate unlocked, Nancy and the rest of the group went to the lab’s front entrance were they met up with Hopper, Joyce, Mike, and Will. The group then traveled back to the Byers’ house. Once it was determined that they’d have to interrogate Will in order to discover the Mind Flayer’s weakness, Nancy assisted in turning the Byers’ backyard shed unrecognizable. During Will’s interrogation, he signaled in Morse code the way to stop the Mind Flayer: closing the Gate. Soon after, the phone in the Byers’ kitchen rang, allowing the Mind Flayer to know their location and send a pack of Demodogs their way. However, Eleven arrived and eradicated them. Together, the group came up with a plan: Joyce, Jonathan, and Nancy would exorcise the Mind Flayer from Will's body while Eleven and Hopper would go to the lab and close the gate. After taking Will to Hopper's cabin, Joyce, Nancy, and Jonathan restrained him, surrounding him with numerous heaters. This eventually caused the piece of the Mind Flayer possessing Will to be expelled from his body. Sometime later, Nancy attended the funeral for Barbara which was held after the revelations forced Hawkins Lab to acknowledge their involvement in the coverup of Barb's death. On December 15, Nancy volunteered at the Snow Ball, serving drinks. She and Jonathan were still together, sharing a smile as Jonathan was taking photographs. When Nancy noticed Dustin sitting on the bleachers alone after being rejected by numerous girls, she offered to dance with him. As they danced, she told him that girls that age are “dumb”, and assured him that in a couple of years he’d “drive them nuts.”

Nancy is highly skilled, in doing detective work. She was capable to reconstruct a crime scene in Heather’s house with Jonathan by in her own mind by looking around at the trail of blood, chemicals, and materials around the scene of everywhere and figured out about the victims and suspects.