After dumping Sibyl and dealing (quickly) with her death, Dorian reads the yellow book for the first time, and is profoundly changed… for the worse.
Dorian kills Basil in a fit of moral-crisis-driven rage, and blackmails Alan Campbell into destroying the evidence.
Dorian's close call with James Vane makes him reevaluate his life—should he in fact be trying to reform himself? He briefly thinks he can be good again, but, alas, he can't. In an attempt to get rid of the evidence of his sins, he slashes the portrait, and dies.