The school's security guard dies, leaving Hae-sung a notebook belonging to his missing father. The revelation is shocking, and he storms the NIS for answers. The answer pushes him away from the mission, and he takes time off. However, he resolves to continue but returns only to discover Soo-ah witnessed it all.

Hae-sung is caught off guard when he recognises Soo-ah's childhood name, Bong-ja, which stirs memories of his first love and distracts him from his focus. Despite the emotional turmoil, Hae-sung pushes forward with the mission to uncover the secrets behind the third ghost story. However, a missing key component forces Soo-ah to join the mission despite Hae-sung's strong opposition to her involvement.

After uncovering the possibility of a mole within the NIS, Hae-sung becomes increasingly distrustful of those around him, causing him to question the mission's integrity. Meanwhile, Soo-ah exposes a secretive scheme within the school that guarantees top grades for VIP students. As the web of secrets deepens, Hae-sung uncovers the connection between the gold bars and Chairwoman Seo, prompting him to vow to end her sinister plans.