Ruby (Seohyun) has a hard time dealing with people. Due to that, she is a recluse and stays at her home only. Ruby looks at Ji-Suk (Lee Yi-Kyung) through her window every day and she likes him even though she has never met him face to face. Ruby supports herself by working as a freelance jewelry designer and she is quite talented at her job. She learns that she won a jewelry design contest which gives the winner their own jewelry line. If Ruby does not attend the award ceremony, the prize will be given to the runner up. On the day of the ceremony, Ruby happens to find a ruby ring that a mysterious man gave to her a month earlier. He told her that the ruby ring would grant her 3 wishes and each wish would last for 3 hours. She changes.
