Despite being teacher and student, and Archie Andrews engaged in an illicit affair. They broke up after Jason Blossom's death, but resumed their relationship after school started again.
They broke up a second time when their relationship was found out and Ms. Grundy was forced to leave town.
Archie first encountered his music teacher, Ms. Grundy, when he spent the summer before his sophomore year working at his father's company, Andrews Construction. This proved to be a defining summer for Archie, as they embarked on an illicit affair.
Archie and Geraldine were at Sweetwater River on July 4th, at the time a gunshot was heard in the area. They later discovered that his fellow student Jason Blossom had died under mysterious circumstances. Fearful that their relationship would be discovered, they promised each other that they wouldn't tell anyone about what they'd heard that morning, in order to keep their relationship a secret, and ended it. Archie was conflicted but decided to keep his mouth shut.
Season 1 EditArchie set up a meeting with Ms. Grundy concerning his interest in music that he developed over summer break. Despite their relationship having ended before school began, Archie attempted to persuade Ms. Grundy to tutor him in music. She was reluctant and tried to put distance between them. At the Semi-formal dance, Archie begged Ms. Grundy once more to teach him, and when he reiterated his promise to stay silent about the gunshot, she eventually relented to tutor him during school hours.
After Jason Blossom's body was found, Geraldine was paid a surprise, late night visit by Archie, whose conscience was eating away at him. They both heard the gunshot on July 4th, at Sweetwater River, it could have been the shot that killed Jason. Geraldine assured Archie that they didn't know anymore than the police, which is that a gun was fired, and Jason was dead, they didm't know by whom though. Archie believed telling them would be of help, as when the shot was fired was something the police aren't aware of, however, Geraldine was adamant he say nothing. She reminded him that both of their lives could be ruined if people find out about their relationship. Matters only got worse, as Archie was questioned by Principal Weatherbee, he didn't say anything to him, but if what he and Miss Grundy had wasn't real, then he didn't know what he was protecting. Geraldine insisted that their relationship was real, so much so that she was putting herself in Archie's hands, and they resumed their relationship. Unbeknownst to either of them, they had been seen by Jughead Jones.
During the Pep Rally, after arguing with Jughead about their affair, Archie approached Geraldine to tell her that he would be coming clean to Principal Weatherbee and Sheriff Keller about the gun shot. Although he respected her choice to stay out of it, he couldn't sit back and do nothing, but would try to keep her name out of it. The next morning, Archie prepared to come forward, however, Sheriff Keller and Principal Weatherbee were more concerned with Cheryl Blossom, as Jason's autopsy had been performed and the evidence and her account of what happened to Jason didn't match up. 
The following morning, after Cheryl had been questioned, Archie finally decided to tell the police that he'd heard the gunshot that morning by the riverside, which according to Cheryl, she and Jason had also heard. However, as promised, he didn't include Ms. Grundy in the confession, his cover story was that he was there with his dog, Vegas, working on some songs that morning. Geraldine and Archie arranged another one of their meetings and discussed why Archie would tell the authorities about the gunshot, he did so hoping that it would help Cheryl, as they were going to crucify her. However, by helping Cheryl, he put himself and Geraldine at risk. Archie attempted to down play the situation but it was far more serious than he was aware. Realising that they were inching closer to being found out, Geraldine decided it was best to suspend their lessons for the time being.
She would then attend the Taste of Riverdale, where she ran into Fred Andrews, Archie's father. Fred told her how Archie spoke very highly of her. He then explained that he wanted to be supportive of his son's music but he first needed to know if Archie had the talent to match his passion, Geraldine assured him that the talent was there, unquestionably.
Archie and Fred Andrews sat in on Geraldine's cello performance. Afterwards, they congratulated her on the beautiful performance, and gifted her with flowers. She thanked them both for coming. In a show of gratitude, for all she'd done for Archie, Fred offered to take her out to dinner. The three ended up at Pop's Chock'lit Shoppe where they were seen by Betty Cooper, who had just caught on to their affair. Betty pulled Archie aside and asked him about his relationship with Grundy and what he really knew about her. The next day, Betty began investigating Ms. Grundy, starting with an interview for The Blue and Gold, as the newspaper was doing a series of articles, spotlighting the teaching staff. Ms. Grundy revealed she had previously done an independent study with Jason Blossom.
Afterwards, Geraldine and Archie spent the night watching old movies and talking, Archie wanted to know more about her. Teaching wasn't always Geraldine's passion, it was performing, following her graduation, Geraldine auditioned at all the major symphonies, however, she never made the cut, and that was the end of that dream. Archie questioned if what they had was a dream, to which she replied, if it was, it's a good dream, then the two of them kissed.
While Archie was with Geraldine, Betty and Veronica Lodge had broken into her car and found a gun and an I.D. card with the name Jennifer Gibson. They quickly told Archie of what they had found. Archie returned to her home the next day, and confronted her about it, asking if her real name was Jennifer Gibson, which she admitted to be true. She claimed she was in an abusive marriage, her aggressive husband would come home drunk, every night. One night, she ended up in the ER with broken ribs and a shattered collar bone. He promised it wouldn't happen again, but it did, so she left him, got a divorce, changed her name, then moved to Riverdale.
Later that night, she received a surprise visit from Archie at the school, he gave her a brand new and expensive cello bow. She believed it to be a goodbye gift, as Archie wanted to end their lessons, but he said it's a don't forget me gift. The two of them were interrupted as Alice Cooper, Fred Andrews and Betty barged into the music room. Alice had read Betty's diary and had learned of their affair. Alice confronted the two about their secret relationship and insisted that they let the law take over, but Archie pleaded with them to come up with another solution. Alice refused to budge. In an effort to protect Archie, Betty claimed she would tell everyone in town that she broke into Ms. Grundy's car, stole from her, and made up the entire story. Doing this would only further perpetuate the negative belief that crazy ran in the Cooper family. In the end, they settled on Geraldine not only quitting her job at Riverdale High School, but leaving town as well. With her belongings packed, Geraldine walked towards her car, prepared to leave, but first stopped to eye two teen boys.
- Jughead: "What do you see happening with Grundy, long-term? What do you want?"
- Archie: "[Sigh] I want to be with her. I don't know how, but I wanna hang on to what we have for as long as possible."
- Jughead: "Yup. I feel that. I'm trying to hold on to something a lot older than me, too."
- ―Archie tells Jughead about Miss Grundy.[src]
- ↑ Aguirre-Sacasa, Roberto (writer) & Krieger, Lee Toland (director) (January 26, 2017). "Chapter One: The River's Edge". Riverdale. Season 1. Episode 1. The CW.
- ↑ Aguirre-Sacasa, Roberto (writer) & Krieger, Lee Toland (director) (February 2, 2017). "Chapter Two: A Touch of Evil". Riverdale. Season 1. Episode 2. The CW.
- ↑ Lawrence, Yolonda E. (writer) & Krieger, Lee Toland (director) (February 9, 2017). "Chapter Three: Body Double". Riverdale. Season 1. Episode 3. The CW.
- ↑ Grassi, Michael (writer) & Piznarski, Mark (director) (February 16, 2017). "Chapter Four: The Last Picture Show". Riverdale. Season 1. Episode 4. The CW.