In this film, the ghouls from Monster High take a trip to the bustling city of Boo York, embarking on an adventure filled with dazzling lights and mysterious occurrences. Cleo de Nile is especially excited about the journey since it involves an extravagant gala where her family plans to unveil a magical comet. Among the excitement, Cleo reencounters her ex-boyfriend, Deuce Gorgon, stirring up old feelings and drama. The group meets Luna Mothews, Elle Eedee, and Mouscedes King—three new ghouls who introduce them to the city's vibrant, diverse nightlife. Amidst the glamor, they uncover an ancient prophecy tied to the comet's arrival, hinting at ominous consequences if not handled correctly.

As their adventure progresses, the ghouls find themselves navigating through not only the glittering city but also a web of secrets and threats. Cleo's sister, Nefera de Nile, complicates matters with her sinister motives revolving around the comet. The team must now work together to decode cryptic messages and prevent impending disaster while balancing friendship dynamics and personal growth. Tensions rise as they face unexpected challenges and adversaries, revealing the true nature of their bond and individual strengths. With time running short, the ghouls are thrust into a race against time to rescue Boo York from potential chaos and ensure their mission's success.