Donghae and Hyukjae have just gotten married but Hyukjae's twin brother Eunhyuk runs into trouble and is forced to move in with Hyukjae and Donghae. All seems okay in the beginning but Eunhyuk's pranks on Donghae at pretending to be Hyukjae keep getting more frequent and more intimate to the point that Donghae feels uncomfortable. Donghae tells Hyukjae to talk to his brother not to joke like that. One night when Donghae had more than enough drinks Eunhyuk takes advantage of that and pretends to be Hyukjae to sleep with Donghae but Hyukjae arrives in time and the brothers get into a fight and Eunhyuk is kicked out of the house. 

Hyukjae has two freak accidents back to back nearly killing him and Donghae is starting to suspect Eunhyuk having a hand in it but Hyukjae thinks is impossible. Donghae starts having Eunhyuk followed and is told how Eunhyuk follows and stalks him everywhere and also about the shady people he's meeting. On Hyukjae's third attempt at being hurt Donghae has no doubt in his mind that it is Eunhyuk trying to murder Hyukjae. Donghae is desperate to save Hyukjae and goes to visit Eunhyuk to beg him to stop but Eunhyuk instead confesses his love for him and begs Donghae to leave Hyukjae. Donghae tells Eunhyuk that there could never be anyone else but Hyukjae. 

Things calm down for a while and Eunhyuk comes back asking for forgiveness, he seems sincere and Donghae & Hyukjae take him back into their home. Donghae feels like something is odd about Eunhyuk but doesn't think much of it any longer as Hyukjae and Eunhyuk seemed like their sibling love is growing and back to normalcy and also because Eunhyuk starts dating Hyoyeon. Everything comes to a screeching halt as Donghae gets a call during a business trip from Hyukjae telling him that Eunhyuk has died in a car accident with his girlfriend Hyoyeon. Donghae rushes back home to accompany Hyukjae during this grieving time. However not very long after Donghae feels that Hyukjae is acting weird but attributes it all to his twin's death but as time progresses there are little things that Donghae notices that are not making sense, like the small encounter they had with an old colleague of Hyukjae's that he didn't seem to recognize, Hyukjae claims that he is suffering from post traumatic disorder from the lost of his brother. Hyukjae promises Donghae that he will get help but Donghae doesn't know what to believe anymore. 

So every night he goes to sleep with the same thought of... who lies in my bed.