After she loses her engagement ring and her phone is stolen during a hotel fire drill, Poppy Wyatt, discovering an abandoned phone in a trash can, crashes into the life of the phone's owner, businessman Sam Roxton, when she uses his phone to make her wedding preparations. He wants his phone back and doesn't appreciate Poppy reading his messages and wading into his personal life. What ensues is a hilarious and unpredictable turn of events as Poppy and Sam increasingly upend each other's lives through emails and text messages. As Poppy juggles wedding preparations, mysterious phone calls, and hiding her left hand from Magnus and his parents, she soon realizes that she is in for the biggest surprise of her life.