Set in the peaceful town of Geumsan. Bo-Mi gets into an hit-and-run accident. The witnesses of the accident are Bo-Mi's grandmother Moon-Hee and her dog Aengja, but Moon-Hee has Alzheimer's disease.

In her mind, Moon-hee is 'Secret Jouju', the princess in TV animation. In reality, Moon-hee is a granny with Alzheimer's disease cared by her son, Du-won and the grand-daughter, Bo-mi. On one secret night-out with Bo-mi, Bo-mi gets a hit-and-run accident. Moon-hee is the only witness, but she rather mumbles the nonsense. Bo-mi stays in a coma and the police can't help. Now Du-won has to track down that culprit with a few pieces of the vehicle and his mother's might-be-meaningful gibberish.