He's petrified, so scared, but it's not because he's surrounded by death eaters. It's because of her. It's because he was there that night. The night that changed his entire life. He witnessed it. Watched it happen and couldn't do anything. He was helpless, a mere infant. He shouldn't remember, but he does.
-Flashback-
He was in his cot, watching as the snitches above his head rotate. That was when he heard the screams and that awful, awful laugh. It was high pitched and maniacal. It is engraved in his memory. It always will be. It's a blur after that of crying and screaming, whether it was him or his parents, he's never sure.
The next thing he remembers he's in the living room and his daddy is rocking back and forwards and his mummy is screaming in pain and there's the laugh again, the awful high pitched cackle. The woman is telling his mummy that he'll be next and mummy is screaming his name "Neville….." and he's sobbing. Then his mummy's eyes close and she goes still. He's scared and screaming for his mummy and the woman turns to him, her wand raised and still cackling. He screams louder as she begins to speak the word that made his mummy scream and his daddy rock backwards-and-forwards,
"cruc-…,"
She doesn't finish the word because there is a bang and people shouting and then there's a loud "crack!" and she and the other people who hurt his mummy and made his daddy rock backwards-and-forwards are gone.
-End of Flashback-
He hears that cackle again now, that awful high pitched laugh that has haunted his dreams for so long. It's her and he wants to kill her. Kill her for what she has done to his parents to make her pay for the way they are now. But a small part of him wants to run away. To scream and cry because he's petrified of her and of that laugh that has haunted him for so long. But he does neither. His friends need him now.
He knows though, that one day she will pay for what she has done. That he or someone else will make her pay.
Because nobody can be that evil, and not have to deal with the consequences, sooner or later.