What is the problem among the young lovers at the beginning of A Midsummer Night's Dream?

At the beginning of A Midsummer Night's Dream, Hermia is in love with Lysander. Her father, Theseus, wants her to marry Demetrius, who has recently courted her best friend, Helena. They all appear before Egeus, the reigning duke, and Hermia's father demands she be put to death, according to the law, if she refuses to marry Demetrius.