Turtles all the way down
(Book)

Solving the mystery of fugitive billionaire Russell Pickett would bring a hundred-thousand-dollar reward, so Aza and her best friend, Daisy, are eager to investigate. They navigate the short distance from their homes in Indianapolis, as well as the broad social divides, that separate them from Russell Pickett's son, Davis. But Aza is living within the ever-tightening spiral of her own thoughts. Still hurting from the death of her father years ago, she's crippled by 'thought spirals' and the irrational, obsessive fear she has of microbes and bacteria.