The dazzling streets of Busan. A healthy and vibrant woman is trying to hail a taxi. A taxi stops in front of her... a high school girl cuts in line, gets in the taxi first, and leaves. But... that very taxi turns out to be owned by a serial killer. The woman and the high school girl who swapped fates... the next day, they are found dead, throwing Busan into chaos. A few days later, the woman hails the same taxi again... in the rearview mirror, she sees the serial killer's eyes...