Perfect Number

Seok-go was a child genius, but now lives an average life as a high school math teacher. When his new neighbor, Hwa-sun, moves into the apartment next door, she becomes his new obsession. One day, Suk-go witnesses Hwa-sun murder her ex-husband during a violent encounter. He puts his math skills to the test as he calculates the perfect alibi for her crime. Thanks to Suk-go's impeccably crafted crime, Hwa-sun even passes the polygraph test and the police have no choice but to let her go. However, the detective assigned to the case, Min-sun, detects something strange and is unable to drop Hwa-sun as his prime suspect.