In Eclipse Rosalie states that her record is better than Esme's so I wondered what happened that Esme slipped up. This was my answer.
I came home from my shift to the sight of Esme packing what few things she had. I gently put my hands on her shoulders and asked "Esme, sweetheart, what's wrong? Where are you going?"
I was very careful to touch her lightly. She was a newborn vampire, only a few months old, and with a recent human life that was very abusive. Those emotions can be magnified during the change to immortal.
I felt her shoulders shake and what could only be described as the sound of sobs coming from her lips. I gently turned her around to face me but she kept her head down and wouldn't look me in the eye. "I'm so sorry Carlisle. I didn't mean to do it. I thought I could do it alone. I was so thirsty and I thought I could just go out into the woods and find a deer or even rabbit to hold me over until you got back."
This didn't sound good, "What did you do Esme? You can tell me, I won't get angry. Just tell me what happened."
She took a deep breath, I'm sure to steady herself. Then looked at me, with the red eyes of a vampire who'd just drank human blood. They had slowly been changing to an orange color but now it would have to start all over again.
"I'm sorry," she said again, "He was a hunter and I lost my focus. I didn't realize what I'd done until after it happened. I killed someone Carlisle. Buried him and rolled a boulder over on the burial so no one would find him. I said a prayer for him and asked God to forgive me. It was an accident; I didn't plan to do it. I'll have to leave now, I don't want to hurt anyone else," she sobbed against me again as a cradled her in my arms.
"Esme, I know you didn't mean to. I share most of the blame here. I was going to take you out hunting when I got back today but we should have gone before I left for work. I waited too long. Our kind get irrational when we get thirsty and we can't control ourselves. I've been doing this so long I forget how it is for you and Edward." Then I thought of something, "Where is Edward? He should have been here with you."
She shook her head, "I sent him to the book store. I thought that if I had something different to read I could distract myself until you got home. He offered to go hunt with me but I didn't feel comfortable dragging him along. He's so sweet but it just makes me feel bad to have him baby-sit me all the time. But apparently I need it."
I held her close and kissed her hair, "It's hard for us to live by human rules. We are designed to do exactly what human laws try to prevent. We are made to kill, but that doesn't mean we have to kill people if we are careful. We will have to move but we need to do it slowly so it looks natural to the humans. Up and leaving right after a disappearance will be more suspicious than if we take it slow."
"You aren't mad at me?" she added looking up at me with confusion in her eyes.
I moved a stray hair from her face, "I'm not mad, you didn't plan to do it and I share the blame for making you go too long. You were running on instinct and thirst. This isn't something you meant to do. Let's go for a walk to where you buried him and I will pray for him as well."
We walked to the burial sight and Esme held tight to me. I knew she was afraid and upset but unfortunately these things happened in our world. I tried to be better than that and was trying to teach Edward and Esme as well but the truth is it was like trying to teach a grizzly bear to be domestic. Even if you started out early there could still be times when the instincts took over and terrible accidents happened. We were vampires designed to kill and I hadn't taken enough precautions to keep that from happening. We came up to the boulder and I checked around to make sure he was buried well enough. I prayed for him and hoped God would hear the prayer of a damned soul for someone else. I took one last look around and something caught my eye. Walking a few yards away I found the poor soul's wallet. The few pictures of his family, wife and two children, stared back at me accusingly. I couldn't let Esme see this or she would forever be wounded.
"What is that?" She asked.
"It's just his wallet, but there was only an address in it. I'll take care of it," I lied to her. It was the only time I ever lied to her. I couldn't stand the idea of making her hurt further for what she'd done. She had so much love to give and would never have children. And for these children she'd accidentally stolen their father away. How was I going to make it right for them?
We walked back to the house and when we got there Edward was waiting for us. He didn't have to ask what happened because he'd already read our thoughts. He looked at Esme and took her hand. "I'm sorry, I should have stayed to help you or to go hunting with you. It may not have gone much better with me but at least you wouldn't have been alone. I share the blame in this too."
Esme shook her head, "I feel so useless. All I do is sit around and think about how thirsty I am."
Edward walked over to a pile of books, "Carlisle and I noticed how much you seem to be interested in architecture so I got you a few books on it. I know it doesn't make up for today but maybe it will help you out in the future and I promise not to leave you alone anymore." He picked up one of the books and brought it over to show her something in it. He was trying to distract her but it wasn't working very well at the moment. It would take awhile before she would overcome this setback; mentally and emotionally.
"Edward," I said in my head, "I have the hunter's wallet with me. We need to get it back to his widow with a trust fund for his family. Don't let Esme know that he had a family. It will only make it worse for her."
He nodded his head without looking at me and without breaking his conversation with Esme. He was a good kid and he cared about her. We had all learned a lesson here today.