Jitarth Jadeja was already deep into conspiracy theories when he first heard of Q. One day in December 2017, he tuned into Infowars, the media outlet run by the conspiracy theorist Alex Jones. Two guests on the radio show were talking about the "calm before the storm," a reference to an absurd theory that President Donald Trump will soon wage a secret war against a cabal of Satan-worshiping pedophiles and a slew of other evildoers. It's one of the many tall tales believed by followers of the movement called QAnon, ranging from the false claim that the government created vaccines...