What destiny does Jack worry about in Lord of the Flies, and what view of the murder does it express in chapter 10?
Jack is worried that the beast will come in disguise again to the tribe. In this chapter, Jack has assumed full authority of the hunters. He sits naked to the waist, has ordered a member of the tribe beaten for some unknown crime, and now commands them to keep watch for Ralph and the others. He believes they will come, which leads to talk of the beast.
“—and then, the beast might try to come in. You remember how he crawled—”
The semicircle shuddered and muttered in agreement.
“He came—disguised. He may come again even though we gave him the head of our kill to eat. So watch; and be careful.”
It is clear that Jack believes Simon was the beast. Or at least, he says that's what he thinks. Like Piggy claiming it as an "accident," Jack may be trying to rationalize Simon's murder. The other boys sense this too. One boy, Stanley, tries to ask about the truth of the circle, and the violence they committed there.
“But didn’t we, didn’t we—?”
He squirmed and looked down.
In the silence that followed, each savage flinched away from his individual memory.
“No! How could we—kill—it?”
Half-relieved, half-daunted by the implication of further terrors, the savages murmured again.
So the boys do recognize what actually happened, but none of them can admit it. Jack turns the conversation once more to the beast, stating that they cannot kill it. This offers some relief for the boys, because it means (in their minds) that they didn't kill anything. Yet it also terrifies them, because it means they have to face the beast again.