Titania falls asleep, Oberon launches his plan, and Robin makes a critical error.
Characters: 
Titania

After falling asleep, Titania is put under a spell by Oberon and will fall in love with whomever she sees when she wakes. 

First Fairy

A fairy who sings Titania to sleep. 

Second Fairy

A fairy who sings Titania to sleep. 

Chorus

Fairies who sing Titania to sleep. 

Oberon

Oberon places the flower nectar on Titania’s eyelids as she sleeps, ensuring she will fall in love with whomever she sees when she wakes. 

Lysander

After being mistakenly drug by Robin, Lysander wakes to see Helena, to whom he professes his love.

Hermia

After spurning Lysander’s advances in order to preserve her honor, Hermia falls asleep and then wakes up alone. 

Robin (Puck)

Robin mistakenly poisons Lysander, making him fall in love with Helena, rather than Demetrius. 

Helena

While chasing Demetrius, Helena discovers a sleeping Lysander, who falls in love with her as soon as he wakes. 

Demetrius

Chased by Helena, Demetrius flees into the woods. 

Scene Summary: 

The fairies sing Titania to sleep. After they’ve gone, Oberon appears with the flower and drops its nectar onto Titania’s eyes. 

Nearby, Lysander and Hermia are also looking to get some sleep. When Lysander lies down next to Hermia, she tries to get him to be a gentleman and sleep farther away. After some back and forth, Lysander moves away — a bit — and they both fall fast asleep. Just then, Puck appears. Thinking Lysander and Hermia are the Athenian couple Oberon mentioned in the previous, scene, he drops the love potion on Lysander’s eyes. 

Demetrius and Helena appear nearby.  Demetrius tries to get Helena to stop following him, and when he ditches her, she notices Lysander on the ground. Lysander wakes up and falls instantly in love with Helena. Helena thinks Lysander is making fun of her, and she decides to leave. Lysander follows her. Just after they’ve gone, Hermia wakes up from a bad dream and notices Lysander is gone. She decides to go and look for him, even if the woods are dangerous.