The truth didn't end at Nova City International Academy.
It only got more dangerous.

Six months after exposing the corruption that rocked NCIA, Han Yoo-na should be healing. Instead, she's haunted by a mystery she can't let go—the unfinished story of Im Soo-hee, a girl silenced by power and buried by lies. But when a cryptic package arrives containing a coded musical score, a faded photograph, and a note that leads to Budapest, Yoo-na and her closest ally, the fiercely talented Kwon Min-jun, are thrust into a new and far more dangerous investigation.

Across the globe, in the hauntingly beautiful heart of Europe, the pair follow Soo-hee's ghostly trail to a long-abandoned academy and a buried Cold War secret. There, among crumbling gothic buildings and layers of history, they discover whispers of something far bigger than a school cover-up—an international web of silence, symbols, and a mysterious operative known only as The Cleaner.

As they race to decode the cipher left behind, Yoo-na and Min-jun must navigate foreign streets, private archives, and their own unresolved feelings. But the deeper they dig, the clearer it becomes: someone is watching. Someone doesn't want them to find the truth. And someone still holds the power to make them disappear.

Because this time, the silence isn't institutional—it's lethal.