Buffy the Vampire Slayer (1997)

S1E1 Welcome to the Hellmouth (1)

As Buffy, a young vampire slayer, attempts to begin anew at Sunnydale High, she uncovers a shocking secret: the school is located above a gateway to a hellish dimension. This revelation complicates her efforts to fit in and lead a normal teenage life while also confronting the dark forces that lurk beneath the surface of her new home.