During a high-stakes exam, Luna anxiously decides to revise her answers after suspecting her sister Aurora copied her work—even her mistakes. Though the proctor declares Luna's paper perfect, Luna insists there is a better solution and races against time to submit hers first. Aurora remains calm, revealing she’s found an improved formula believed unsolvable for years. Suspicion arises as it appears Aurora copied Luna right after she finished. The tension peaks when the exam ends and the proctor announces an investigation to uncover who cheated, leaving the truth unresolved.