Psychological studies have found that repeating an action for twenty-one consecutive days can help change a person's behaviour, such as waking up early or exercising. The idea, extended to matters of love, evolves into the 21-Day Theory: the belief that if you pursue someone for twenty-one consecutive days, you'll win their heart. But what happens when a woman uses the 21-Day Theory in an attempt to turn a gay man straight? 
A woman has had a crush on a wealthy and seemingly perfect man who's remained single for a long time. Rumors swirl about his sexual orientation, but she refuses to believe them. He never confirms or denies the speculation that he's gay. Determined to uncover the truth for herself, she employs the theory to pursue him.