Though Cheryl Cooper wrestles with her own mixed feelings about Valentines Day, she wants to make sure her good friends Naomi and Seth Miller have the truest love possible which doesn't include the obvious tension that is building between them. So when Cheryl stumbles across clues that indicate Seth is keeping an odd secret, and he gets testy and elusive whenever she asks him about it, her mystery-solving radar kicks in. Candy-heart messages left for her to find begin to make sense. Without knowing who her accomplice is, she follows cryptic leads to discover what happened in a split-second one summer day, decades ago, which splintered friendships and fostered love.