Doppelgangers. Mice that take the form of humans. With murder intent, the look-alikes and the originals are both pressured to fight in their own ways. After an ambiguous event in their life, Ji-Suk and So-Hee's love life has been shattered. While trying to reconcile with her, Ji-Suk meets her look-alike, and that's how this story starts. What will he do when he, too, has a look-alike destined to kill him? And what's the secret So-Hee will never tell?