Ellie Hawthorne's event-planning business desperately needs a jolt of life. Determined to drum up leads, she heads to Las Vegas for a trade conference - and has one too many shots of tequila. The next morning, Ellie wakes up with a ring on her finger and next to the last person she expected to see again: Connor Grayson, the high-school boyfriend who broke her heart.

Connor is in Vegas to secure funds for his self-driving car project. He's as shocked as Ellie is by their accidental marriage. But when he finds out that his beloved grandmother Viola has suffered a heart attack, he begs Ellie to keep up the charade - just until Viola recovers.

Neither of them could have guessed what Viola has planned. And Ellie starts to think that maybe she got luckier in Vegas than she could have ever imagined. With a little help from Viola and four elderly Elvis impersonators, can these former sweethearts find lasting love?