Mr. Frank, a QAnon influencer whose Facebook page in recent months has shown him pictured with such conservative celebrities as Donald J. Trump Jr., Michael Flynn and Sidney Powell, has fashioned his team into a new style of border enforcers, motivated not so much by halting immigration as by guarding the country from other perceived threats — in this case, an unfounded conspiracy theory that migrant children are being funneled into pedophilia rings.

“They are being trafficked, sex trafficked. That’s the No. 1 trade,” Mr. Frank, 44, said as he name-dropped from his list of purported conspirators, starting with the late Jeffrey Epstein. “The money, that’s where it’s at now,” he said…

“We haven’t heard about migrant children brought in to be sex workers or slaves,” said Stacey Sutherland, an official with the Arizona Anti-Trafficking Network. “At the border, it’s overwhelmingly people who paid to be smuggled.”