Thsi incident occurs in Chapter 10 of the novel, and it is after Jack has effectively seized power of the boys, and Ralph is left with Sam and Eric and Piggy, and they are trying to keep a signal fire going on the beach themselves. However, they face a number of problems. Firstly, there are only 4 of them, and Piggy with his asthma is not able to help collecting wood. Secondly, all the wood they can find is wet and rotten, which means that to keep the signal fire going involves constant attention and a constant search for more timber, which is more than they can do. Sam and Eric are clearly exhausted and they protest that they are unable to find any more wood, especially at night.
Piggy therefore suggests that they light the fire every morning, because, as he says, "Nobody ain't going to see smoke in the dark." Ralph's reaction to this is one of acceptance. Although he wishes for a fire for comfort at night, he agrees with Piggy and the twins: "Ralph stood up, feeling curiously defenseless with the darkness pressing in." Arguably, this feeling that Ralph has could be considered a foreshadowing of the attack of Jack and his tribe when they seize Piggy's glasses - and very significantly, they completely ignore the conch.