In Act 3, sc. 2, Puck tricks Lysander and Demetrius into thinking each one heard the other's voice, causing them to tire themselves out by chasing the imaginary. Soon after they fall asleep, Helena and then Hermia enter the area and both of them are tired from the all-night chasing around, so they both fall asleep. Puck then annoints only Lysander's eyes with the nectar from the flower because Demetrius already having been annointed, has fallen in love with Helena. Lysander though, needs to fall back in love with Hermia, so he is the one Puck annoints. At the end of the act, all four lovers are sleeping. In Act 4, sc. 1, Oberon, having gotten possession of the changeling child that he wanted, tells Puck to remove the spell from Titania and the ass-head from Bottom. Along with this returning to right, he tells Titania that they will put the four human lovers into a deep sleep so that when they awaken, they will think all their memories were merely a dream. When Theseus, Hippolyta and the others come in to the scene in Act 4, the four lovers awaken and Lysander, seeing Hermia first upon waking, falls in love with her again, so now that couple is back together and Demetrius and Helena are a couple. All is well.