The truth about Lockhart also is revealed in this chapter, when he nervously edges out of the staff room when given free rein to tackle the monster. He confirms Ron and Harry's suspicions that he is a phony when he is packing to leave so as not to face the monster, and we know immediately that the defense against the dark arts post will be left open again (in the first book of the series, the defense against the dark arts teacher has to leave for being affiliated with Voldemort). Lockhart is utterly useless and actually detrimental to Harry and Ron as they venture into the tunnels to confront the basilisk, and luckily his role in the plot is made fair when he casts a memory- obliviating charm that backfires, leaving him blithering idiotically to himself. He gets what he deserves during this scene, and his punishment fits his crime.
Finally, Ginny has been unduly frightened by the attacks over the course of the year, and Percy has been upset about her terror and nightmares. In this chapter, we see that Ginny did in fact know something about the attacks, or else she, a pure-blood young witch, would not have been taken into the Chamber of Secrets. We also learn over breakfast that Percy has something he is hiding, suggesting that he is not the perfect prefect he wants everybody to believe he is. Perhaps she could have been saved had she been given the chance to confide in Ron and Harry, or perhaps not. At any rate, Percy is absolutely distraught by her disappearance, as could be expected. When Harry and Ron set down the tunnels to rescue Ginny and save their school, the revelations caused by all of these events shape their journey.