In Lord of the Flies, what is Phil's dream?

From the text:

"Last night I had a dream, a horrid dream, fighting with things. I was outside the shelter by myself, fighting with things, those twisty things in the trees."
He paused, and the other littluns laughed in horrified sympathy.
"Then I was frightened and I woke up. And I was outside the shelter by myself in the dark and the twisty things had gone away."