Hermia's father Egeus wants her to marry Demetrius, even though she wants to marry Lysander. Egeus thinks that Lysander has put a spell on Hermia, to make her love him. After he thinks that he goes to the duke of Athens and says that Hermia will marry Demetrius or she will suffer the consequences. The consequences are she marries Demetrius or Egeus will kill her.
It was all a dream...
The fairies gave Lysander and Demetrius a love potion when they were sleeping, so that when they woke up they would love the first person they saw. When Lysander woke up he saw Helena and so did Demetrius. It created a conflict because Hermia and Lysander ran away from Athens so they could get married, and now their whole plan is ruined and Hermia is sad and heartbroken. Hermia is also mad at Helena because she thinks she is doing something to make them love her more. Helena is mad because she thinks they are all mocking her.
Fairies to the rescue
Lysander and Demetrius love Hermia, and they both want to marry her. Egeus likes Demetrius better, so he orders Hermia to marry Demetrius. Lysander and Hermia love each other, so Hermia doesn't want to marry Demetrius. Demetrius and Lysander argue over Hermia and Lysander says he deserves her. When they have the love potion Demetrius and Lysander fight over Helena and they are always arguing with each other about who they love more.
Hermia, Lysander, Demetrius, and Helena all fall asleep on their way back to Athens. The Fairies undo the love potion on Lysander, but keep it on Demetrius. When they all wake up Lysander and Hemia love eachother and Demetrius and Helena love eachother. Egues and Theseus run into them as they wake up and the resovle the conflict by letting the couples marry. Hermia and Lysander now get what they want and can marry each other. Demetrius and Helena will now get to marry eachother and nobody will fight eachother and they get to do what they wished for.
The fairies realize that what they did was wrong, so they decided to fix it. When they all fell asleep the fairies reversed the potion on Lysander, so that when he woke up he would go back to loving Hermia. They also put a potion on all of them to make them all think it was a dream. They kept the love potion on Demetrius, because Helena truly loves Demetrius and Demetrius will now love her. Since they fairies did that they are all done fighting and they get to do what they all have been wanting to do and marry each other.
Was this all a dream?
As they all wake up after being under the love potion they think that it is all a dream. Lysander's love potion is reversed and he goes back to loving Hermia, Demetrius still has the love potion and now loves Helena. Demetrius and Lysander don't fight over the girls anymore because they love someone different. The both get what they want and get to marry the person they love.
I get to marry Hermia and now you get to marry Helena!