Harry and the others went down into the Black Lake together on the afternoon of the second-to-last day before the Easter holidays.
It was an unpleasant experience.
Without Dumbledore putting in a word for them this time, the fish-folk did not welcome outsiders like Harry and the others at all, so they encountered quite a few complications along the way.
Fighting a tribe of fish-folk underwater was not a good choice, so Harry and the others eventually chose to retreat.
Then, after taking a long detour, they reached the square beside the cliff at the bottom of the lake.
However, what they had hoped for did not happen. Neither Harry and Qiu nor Lavender and Ron, nor even Hermione and Cedric, who gave it a try despite their intense embarrassment, felt anything special at all.
This left them a little disappointed, but not particularly surprised.
Back on shore, they began discussing it.
"I think it makes sense that Lavender and I didn't get a reaction. After all, we're both Gryffindors. My guess is that the legacy a Founder left behind can only be unlocked by students from their own house..." At this point, Ron glanced at Harry and Qiu, then added,
"At least one of them has to be a Ravenclaw."
"It's much the same for Qiu and me." Harry nodded.
"As for why it didn't work for Diggory and Hermione, I'm guessing it's because you two aren't a couple," Qiu said with a smile. "Diggory, you could write to that girlfriend of yours, then try it together. Perhaps that would work."
"Well, um..." Unsurprisingly, Cedric's face reddened again. That was the trouble with having pale skin: even the slightest blush was obvious. Still, he shook his head and said regretfully,
"Qianqian has been working on some very important research