Watch Online Free on Watchseries. Young-bi, who dances well and dreams of becoming an idol singer, Hae-yul, who dreams of becoming a star YouTuber, and Bora, an honor student who has just fallen in love for the first time, are friends of the same high school dance club. One day, they watch a video of a mission challenge where their wishes come true if they dance along in the video application "Dingdong Challenge." The three members who follow the mission dance in their own desires... As a result, death shadows begin to cast in front of them one after another.