The Picture of Dorian Gray is the story of one beautiful, innocent young man's seduction, moral corruption, and eventual downfall. We meet our three central characters at the beginning of the book, when painter Basil Hallward and his close friend, Lord Henry Wotton, are discussing the subject of Basil's newest painting, a gorgeous young thing named Dorian Gray. Basil and Henry discuss just how perfectly perfect Dorian is – he's totally innocent and completely good, as well as being the most beautiful guy ever to walk the earth. Lord Henry wants to meet this mysterious boy, but Basil doesn't want him to; for some reason, he's afraid of what will happen to Dorian if Lord Henry digs his claws into him.
However, Lord Henry gets his wish – Dorian shows up that very afternoon, and, over the course of the day, Henry manages to totally change Dorian's perspective on the world. From that point on, Dorian's previously innocent point of view is dramatically different – he begins to see life as Lord Henry does, as a succession of pleasures in which questions of good and evil are irrelevant.
Basil finishes his portrait of Dorian, and gives it to the young man, who keeps it in his home, where he can admire his own beauty. Lord Henry continues to exert his influence over Dorian, to Basil's dismay. Dorian grows more and more distant from Basil, his former best friend, and develops his own interests.
One of these interests is Sybil Vane, a young, exceptionally beautiful, exceptionally talented – and exceptionally poor – actress. Though she's stuck performing in a terrible, third-rate theatre, she's a truly remarkable artist, and her talent and beauty win over Dorian. He falls dramatically in love with her, and she with him. For a moment, it seems like everything will turn out wonderfully. However, this is just the beginning of Dorian's story. Once he and Sybil are engaged, her talent suddenly disappears – she's so overcome with her passionate love for Dorian that none of her roles on stage seem important to her anymore. This destroys Dorian's love for her, and he brutally dumps her. Back home, he notices a something different in his portrait – it looks somehow crueler. In the meanwhile, the distraught Sybil commits suicide, just as Dorian decides to return to her and take back his terrible words.
Sybil's suicide changes everything. At first, Dorian feels horrible – but he rather quickly changes his tune. On Lord Henry's suggestion, Dorian reads a mysterious "yellow book," a decadent French novel that makes him reevaluate his whole belief system. The protagonist of the book lives his life in pursuit of sensual pleasures, which intrigues Dorian. From this moment on, Dorian is a changed man.
Dorian starts to live as hedonistically as his wicked mentor, Lord Henry, does. The only thing that documents this turn for the worst is the portrait, which alarmingly begins to exhibit the inward corruption of Dorian's soul; the beautiful image changes, revealing new scars and physical flaws with each of Dorian's dastardly actions. As years pass, the man in the picture grows more and more hideous, as Dorian himself stays unnaturally young and beautiful. Rumors start to spread about the various people whose lives Dorian has ruined, and his formerly good reputation is destroyed.
On Dorian's 38th birthday, he encounters Basil, who desperately asks his former friend if all the horrifying rumors about him are true. Dorian finally snaps and shows Basil the portrait, in which the horrible truth about his wicked nature is revealed. Basil recoils, and begs Dorian to pray for forgiveness. In response, Dorian murders Basil, stabbing him brutally. He blackmails another of his former friends into disposing of the body.
Dorian retreats to an opium den after dealing with all of the evidence, where he encounters an enemy he didn't know he had – Sybil Vane's brother, James. Through a rather complicated turn of events, James (who's on a mission to punish Dorian for his mistreatment of Sybil) ends up dead. Dorian isn't directly responsible, but it's yet another death to add to Dorian's tally of life-wrecking disasters.
Dorian is relieved that his enemy is out of the way, but this event sparks a kind of mid-life crisis: he begins to wonder if his vile but enjoyable lifestyle is worth it. He actually does a good(ish) deed, by deciding not to corrupt a young girl he's got the hots for, which makes him question his past actions even more. Seeking some kind of reassurance, Dorian talks to Lord Henry, who's not any help at all, unsurprisingly. Dorian even practically admits to murdering Basil, but Henry laughs it off and doesn't believe him.
That night, Dorian returns home in a pensive mood. Catching a glimpse of himself in the mirror, he hates his own beauty and breaks the mirror. Again, he vows to be good, but we find out that his various crimes don't really haunt him, because he doesn't consider them his fault. Instead, he selfishly wants to be good so that the painting will become beautiful again. Heartened by this thought, he goes up to see if his recent good deed has improved the painting – in fact, it only looks worse. Frustrated, Dorian decides to destroy the picture, the visible evidence of his dreadful crimes, and the closest thing to a conscience he has. Dorian slashes at the painting with the same knife that killed Basil, trying to destroy the work as he did the artist.
A tremendous crash and a terrible cry alert the servants that something very, very bad has happened – it's even audible outside the house. Finally, they go upstairs to check it out, and are horrified by what they find: a portrait of their master, as beautiful as ever, hangs on the wall, and a mysterious, grotesquely hideous dead man is lying on the floor with a knife in his heart. Upon close examination, the rings on the dead man's hand identify him as Dorian Gray.