The young woman with long pink hair claimed to be from Washington state. One day during the summer of 2020, she walked into the Chinook Center, a community space for left-wing activists in Colorado Springs, Colorado, and offered to volunteer. “She dressed in a way that was sort of noticeable,” said Samantha Christiansen, a co-founder of the Chinook Center. But no one among the activists found that unusual or alarming; everyone has their own style. They accepted her into the community. The pink-haired woman said her name was Chelsie. She also dropped regular hints about her chosen profession. “She implied...