The present Kim TaeYeon wish to save her first love from death until she met her future lover way back from the past.  

Tiffany Hwang, the only heir was diagnosed with Intellectual Disability (ID) so her father hired the specialist doctor Kim TaeYeon to treat her daughter.

During the Joseon era, the story about the Crown Princess was arranged to be married to Lord Baek's son and the wedding will take place before the first crescent moon of the month but she secretly harbors feeling towards the late General's daughter who's also her bodyguard. An unfortunate event happens when the King sends General TaeYeon to a great war but she, unfortunately, dies until she begged to the Moon deity to gave her a chance to see the Princess herself before the Deity turns her in

“Sometimes good things fall apart so better things can fall together.” - Marilyn Monroe