Tati is in love with Marcelo, a guy who enjoys dating lots of girls. Honest to a fault, Tati wears her heart on her sleeve, but her intense affection only drives Marcelo further away. After attending a lecture by a young biology professor named Conrado, she decides to put his controversial theories into practice in her own love life. Conrado has developed a scientific guide to seduction, inspired by Charles Darwin's theories, comparing the dating behaviour of young people to that of animals in nature. Tati becomes his eager test subject. At first, the experiment seems to be working: Marcelo is showing interest again. But things take an unexpected turn when real feelings begin to spark between the professor and the student.

Tati and Conrado travel to Cancún, where he's attending a conference to launch his new book. But for Tati, the trip has an extra purpose: she plans to propose to him. During this special moment, with family and friends watching live online, Conrado responds by saying he'd "like to think about it". Tati's disappointment opens the door for renewed hope in her ex, Marcelo, who shows up to find her. To complicate matters further, Conrado's ex, Ângela, is also in Cancún, attending the same event.