汝玉（姜京勋 饰）是一位独自抚养一双儿女的中年教师，她亲眼目睹学生们从自己任教学校的楼顶坠亡。当她发现女儿惠贞（沈秀彬 饰）也在现场时，便反复追问真相，但惠贞只是重复同一句话：“天上有一只鸟。”随着离奇难解的死亡事件接连发生，汝玉与一名跟踪报道此案的记者，以及一位经营观鸟频道的直播主，一同前往鸟类的栖息地。

Yeok, a middle-aged teacher raising a son and a daughter alone, witnesses students fall to their deaths from the rooftop of the school where she works. Discovering that her daughter Hyejeong was also present at the scene, she presses her for answers, but Hyejeong only repeats the same words: 'There was a bird in the sky.' As the strange, unexplained deaths continue, Yeok, together with a reporter covering the case and a streamer who runs a birding channel, head towards the birds’ habitat.