They perform some more magic tests and run out of mana and recover mana and perform more tests and a second sleepover could be fun but it's decided that people can do coordinated tests in their own places and there is not actually a need for them to all be in the same place. The Maxwells' driver takes Jess home (and Maya, too, if she prefers that to staying with the Maxwells but they assure her she's welcome to stay there), then takes Sadde, Theo, and Tyler to the Farron residence, where Sadde prefers to be dropped—he'll go to his place by public transportation, he'd like to talk to the—twins?—yes, thank you, it was a pleasure meeting you.
"Do you have suggestions for how? Other than generally looking for magic I'm not sure a spell that looks for an arbitrary sorcerer clan would work—but I guess it might."
"High concentrations of people who write mysterious words on paper and then– chant? Discarding any obvious false positives, at least until the others are ruled out. I'm not sure what's involved in magic, nor why you wouldn't just be able to check for magic itself."
"Well, Theo can use his meditation to check for magic itself, and we never did find other non-card magic anywhere, is why I'm dubious."
"If Yue is named in Chinese then it's possible that all the sorcerer clans are, in fact, in or around China."
"There are sorcerer clans outside of China, Clow Reed's father was an English sorcerer."
"… Would you be doing it to get information from him or are you just assuming you'd meet him if you went there?"
"The latter. It is a really really tiny village and he was pretty socially affluent there."