Jenůfa is keeping secret from everyone that she is pregnant by Števa, whom she loves despite his drinking and womanising. Jenůfa’s stepmother, the Kostelnička, had a violent, alcoholic husband and tells Števa he won’t be allowed to marry Jenůfa unless he stays sober for a year. Števa’s overbearing behaviour towards Jenůfa angers Laca, who loves Jenůfa and is jealous. When Jenůfa defends Števa, Laca becomes enraged. They struggle and he slashes her face with a knife.  

Months later, the Kostelnička and Jenůfa conspire to keep the birth of Jenůfa’s illegitimate baby secret. Števa knows he has a son, but refuses to marry Jenůfa now her face is disfigured. Laca offers to save Jenůfa’s reputation and marry her, but is reluctant to take on Števa’s child. The Kostelnička tells both Laca and Jenůfa that the baby died while Jenůfa slept. But on Jenůfa’s wedding day the terrible truth is revealed.