Past (Joy Lerner) is a secondary villain in the movie Monster High: Haunted. She is one of the hall moanitors (monitors, who are actually metaphors for corrupt prison guards, police, or government agents) at Haunted High, working for Principal Revenant. Due to her job, she gives dentention chains to "misbehaving" kids (also fitting her grandmother-like appearance) and along with Present and Future, kidnaps the Monster High students. We first see Past and her cronies target Porter Geiss, who has started a resistance movement and has graffitied anti-corruption messages on the wall. The Hall Moanitors catch him in the act and shackle him after he crashes into Spectra, who thought to find a scoop in the ordeal. When Spectra explains she is not a student at this school and is from Monster High, Revenant has the rules changed and unveils her friends as solids. They flee, pursued by the Moanitors, who discover the chains do not work on solids. They safely arrive back at Monster High, but Spectra is chained and dragged back to Haunted High. Dragged into Revenant's office, Spectra asks about the hauntings, which the principal denies. She is given 10,000 essays to do twice as her punishment, which she takes in her stride as she loves writing, which greatly puzzles Porter. Spectra and Porter begin to bond, and when Porter questions all the rules and detentions, he and Spectra decide to investigate. Meanwhile, the Hall Moanitors move into Monster High and begin to seize the ghost students at the school, such as Operetta, Scarah, and Johnny. Re-arriving at Haunted High, the ghouls meet Vandala and Kiyomi, who help them control their ghost forms. Rochelle especially enjoys the freedom with this form and dives into the school pool. Overhearing ghost students talk about how solids want to haunt them, Spectra becomes outraged, labeling the talk as stupid gossip. Spectra realizes this is the exact sort of gossip she spreads and how it is hurtful. The Moanitors behavior escalates, and they begin to give out chains for seemingly no reason at all. When this happens to Kiyomi, the ghouls protect her, bringing them to Revenant's attention. Seeing how the ghouls have become ghosts, Revenant demands to know how they did so, and when they refuse, gives the Moanitors permission to shackle them. Kiyomi protects Draculaura, and Porter takes them to a safe room only he knows of. Spectra admires the artwork, and Draculaura comes to the realization that Kiyomi is the one who has been spying on her. Kiyomi feels bad for this, and when Spectra announces her intention to confront Revenant, Porter pleads with her not to, drawing the attention of the others.
Spectra eavesdrops on Revenant's plan to get more students stuck at Haunted High and is discovered by one of the Hall Moanitors. Revenant questions Spectra until Porter appears and distracts her, giving Spectra a chance to escape, although it means Porter is heavily chained. She forces him to reveal their hiding place by tightening his chains, and the Moanitors capture all the ghouls, causing Spectra to be angry at Porter for selling them out. However, Porter reveals he stole the keys to the chains and transfers all the chains to himself. While Porter had stolen something, so had Revenant, the item being the notebook Clawdeen used to document their journey to give to Spectra for her blog, to use as a true story instead of gossip. From this, she discovers the Boogey Sand, and the Moanitors take off on River's yacht to find it. Now freed, the ghouls pursue them on Vandala's ship after rescuing the rest of the Monster High students incarcerated at Haunted High.
Spectra stays behind, however, to hear Revenant's announcement and her intention to use the Boogey Sand on solids as revenge for making the ghosts fear them. Spectra seeks solace in the library and suddenly realizes Revenant is the Red Lady of legend, as she sends the Hall Moanitors to do her work and never leaves the building.
Kiyomi opens a portal, and they beat the Moanitors to MH, who begin to unleash Boogey Sand via confetti cannons on the Monster High students. Vandala boards their ship, however, and retrieves the sand. Back at HH, Spectra reveals that Revenant is the Red Lady. Taking this in her stride, Revenant seizes the key and sends all the chains flying at Spectra.
Chased by the Moanitors, Kiyomi attempts to open a portal to send them back to the ghost world, and with the help of the others and their ghost powers, is successful. The yacht appears as Revenant's sends her chains flying, and they entangle the boat and Moanitors.