The twins are embarrassed at taking part in Simon’s death, so they pretend they were not there.
Simon dies after the boys have a ceremonial dance during the pig roast and accidentally kill him, mistaking him for the beast. It is a result of their over-exuberance and Jack’s gang’s savagery. Piggy, Simon, Ralph, and the twins were supposed to be above all of that, but they were drawn in by the smell of the meat and the attraction of the barbarity.
All of the boys are embarrassed and overwhelmed with Simon’s death, so they pretend they were not there the next day. When Ralph and Piggy run into the twins, they pretend that they were not really there.
“We just been in the forest—”
“—to get wood for the fire—”
“—we got lost last night.”
Ralph examined his toes.
“You got lost after the. . . ”
Piggy cleaned his lens.
“After the feast,” said Sam in a stifled voice. Eric nodded. “Yes, after the feast.” (Ch. 10)
The boys all realize that they are supposed to be the civilized ones. Now they have an unspoken agreement to pretend that nothing happened. They are all awkwardly lying to each other, pretending that they were not there and did not take part in Simon’s murder.
Ralph is the one that does not want to just let things go. He is very disturbed by “what they did.” He seems traumatized, rocking backing and forth.
“Look, Ralph. We got to forget this. We can’t do no good thinking about it, see?”
“I’m frightened. Of us. I want to go home. Oh God, I want to go home.”
“It was an accident,” said Piggy stubbornly, “and that’s that.” (Ch. 10)
The irony of this is that while Piggy keeps insisting that they should ignore what happened, he will become a target himself next. Piggy does not want to tell Samneric that they were there, but Ralph knows that all of them were.
Piggy’s insistence that they hold on to the fantasy that everything is all right shows that he is desperate for stability, even though the group is losing it. Ralph, on the other hand, is aware that civilization has completely broken down. As the group's leader, he takes personal responsibility for Simon's death, acknowledging that the breakdown in the group is his fault. He feels this failure deeply.