What happens between Helena and Lysander in the woods in a midsummer's night dream?

Lysander is going Into the Woods with Hermia to get out of Athens so they can elope. Helena is following Demetrius, who is following Hermia. Puck is instructed to put the love-drug in Demetrius's eyes but he mistakenly gets Lysander instead. Lysander is wakened by Helena and immediately falls for her. She doesn't have much self-esteem, however, and so assumes that he is making fun of her, and tries to persuade him to go back to Hermia. Fortunately Puck rectifies his mistake by giving Lysander the antidote after he falls asleep.