Nina Hernandez was among the guests at the party, with one of the Eagle siblings and player character questioning her alongside Linda Harper regarding what they witnessed. During the encounter, Nina expressed disregard for the theft, stating that Amy simply "lost one of her baubles". She also spoke of a discussion she had with Linda on what they would do with such a valuable tiara, stating that she'd sell it to finance training for the Olympics due to winning a 400 meter dash state championship in high school.
Later on, however, the evidence collected by the Eagles and player revealed the tiara thief was none other than Nina, who used her costume to avoid suspicions. In preparation of her greedy plan, Nina wore a clown costume under her gorilla costume, taking off the first costume and leaving it hung up in the cloakroom before snatching Amy's tiara. After fleeing the party area, the evil Nina opened a window in a back room before hiding in the cloakroom, where she put her gorilla costume back on to make it appear she had been searching for the thief in the back rooms. A photo of Nina in her gorilla costume proved her guilt, as part of the blue-and-white checkered clown costume could be see poking through a hole in the shoulder. Nina's athletic backstory (which likely served as her motivation for the theft) also coincided with multiple eyewitness accounts that the thief was a fast runner. After the police found the Blue Spider tiara in Nina's house, the villainess was arrested for the theft.
- Nina Hernandez appeared in both Book 1 and Book 2 versions of "Case of the Midnight Masquerade", with Book 2 being the version containing Nina's villainous reveal.