Dorian and his aristocratic friends are at his country house at Selby. Among his guests are the Duchess of Monmouth, her husband, Lord Henry, and Lady Narborough. They're all having tea and lounging around, generally being fabulous.
Lord Henry comes over to chat with the Duchess (whose name is Gladys) and Dorian. They banter about aesthetics—you know, the usual.
Dorian goes off to fetch some orchids for the Duchess, and she and Henry keep chatting. He accuses her facetiously of flirting too much with Dorian. For the first time, we seem to have met a woman who can keep up with Dorian and Henry.
The two of them hear a groan and a thud from the other end of the conservatory. Everyone is startled, and Lord Henry rushes over to see what happened: he finds Dorian, collapsed face downwards.
The guests carry Dorian to a couch, and he comes to after a little while. He's obviously shaken up, and is still distraught. Henry, worried, tells him he should rest and not come down to dinner, but Dorian would rather be with the rest of the party than stay alone.
The reason for Dorian's collapse, we learn, was that he saw a terrifying sight through the conservatory window—James Vane.