Maddie and Nate were high school sweethearts who broke up when Nate left for college. Maddie stayed in their hometown and opened a cupcake shop, working hard to make it a success. Nate became a successful surgeon and was invited back to the hospital in their hometown to give a lecture.
When Nate and Maddie meet again, there is tension between them. Nate is surprised and hurt that Maddie never left their hometown, while Maddie is still hurt that Nate left without saying goodbye. Despite their initial awkwardness, they eventually begin to reconnect as friends.
Maddie is struggling to secure funding to expand her cupcake shop, and Nate offers to help her. As they work together, they realize that they still have feelings for each other. Nate is torn because he has been offered a job in Boston, but he doesn't want to leave Maddie again.
Just as they are about to rekindle their romance, Nate receives an offer he can't refuse in Boston. Maddie is heartbroken, but she knows that Nate can't turn down the opportunity. She returns the promise ring he gave her long ago and prepares for the grand reopening of her shop.
Nate soon realizes how much he left behind in their hometown and how much he misses Maddie. He must decide if his future lies in Boston with work or in his hometown with Maddie. In the end, he chooses Maddie and returns to their hometown to be with her.
Together, they open a new bakery and continue to build their relationship, knowing that love can conquer distance and difficult decisions. The Sweetest Heart is a heartwarming love story about second chances and the power of following your heart.