The narrator tells us that Daniel acted weird on the stairs not because he was weirded out by Gwendolen, but rather because he was on his way to go see his mom for the second time (so we're sort of skipping around in time here).
Now, we are back in the present. Daniel has just left his mom. He is lost in thought, thinking about going to the synagogue and whether or not he'll see the Grandcourts again.
Daniel asks the porter at the hotel which room is the Grandcourts'. He tells Daniel where they're staying but says they've gone out sailing.
Daniel walks around and notices a crowd gathering. They're all watching a sailboat being brought in. Someone mentions that someone had drowned. Someone says it was a man. Someone else says it was a woman. Daniel is overwhelmed with fear and worries if it was Gwendolen who drowned.
Then Daniel sees Gwendolen. She's drenched and shivering.
She sees Daniel and says, "It is come, it is come! He is dead!" (55.8).
Daniel tells the people helping Gwendolen that he is a connection of hers and that he'll take care of everything from here. He gets her some medical attention and telegraphs Sir Hugo, telling him to get in touch with Gwendolen's family.