There are three major events or conflicts in the book, which contribute to the overall plot of the book. The three being Sibyl's death along with Dorian's lack of sympathy, the changing of the portrait and lastly the fast foreword of the book by 18 years.
In the beginning of chapter nine Basil had entered Dorian's home hoping to console Dorian due to the suicide of Sibyl Vane. Dorian took the situation very lightly and treated it as just another chapter of his life. He sees the death as being an artistic expression, which I think is absurd. "And besides, my dear old Basil, if you really want to console me, teach me rather to forget what has happened, or to see it from a proper artistic point of view." (pg 124, Dorian Gray) Basil was sort of taken a back from what Dorian had said because it was as if " you had no heart, no pity in you."
(pg 122, Basil) He knows who had done this to Dorian and whom that made him so cold hearted. " It is all Harry's influence. I see that." (pg122, Basil) Basil knows from the day he had met Dorian, he was a very impressionable individual and worships Lord Henry's every word. Basil knew that Lord Henry had told Dorian to forget about Sibyl and move on with life. "Don't waste your tears over Sibyl Vane." (pg 117, Lord Henry) This discussion about Sibyl's death and Lord Henry's influence sort of foreshadowed the events to come. Dorian was very stern and rude to Basil and treated him as an unworthy friend. This is the reason for him to loose contact with Basil for 18 years. As for Lord Henry, Dorian was very kind and attentive with him,