Im Yoona has never felt luckier. She is about to marry her ideal man, Lee Donghae, but in one afternoon her “happily ever after” begins to fall apart. Not only has she lost her engagement ring in a hotel fire drill but in the panic that follows, her phone is stolen. As she paces shakily around the lobby, she spots an abandoned phone in a trash can. Finders keepers! Now she can leave a number for the hotel to contact her when they find her ring. Perfect!
 
Well, perfect except that the phone’s owner, businessman Choi Seunghyun, doesn’t agree. He wants his phone back and doesn’t appreciate Yoona reading his messages and wading into his personal life.
 
What ensues is a hilarious and unpredictable turn of events as Yoona and Seunghyun increasingly upend each other’s lives through emails and text messages. As Yoona juggles wedding preparations, mysterious phone calls, and hiding her left hand from Donghae and his parents . . . she soon realizes that she is in for the biggest surprise of her life.