Flashback to 1991. Minnesota winters are long and cold, physics professors are all male, and information is found in the library - whether it's clues to a homework problem, how to fix a furnace, or skeletons in colleagues' closets. Lori Barrow has just turned 17, and she starts out her graduate career on the right foot, immediately passing the qualifying exam that's slated to eliminate at least half the class. But she soon learns that academic challenges are the easiest part of getting a PhD. By the end of the first month, none of the new students trust each other, but no one expects it to lead to murder. When one of their classmates is found dead in front of the department's Foucault pendulum, the police focus on all the wrong suspects. It's up to the students to put their homework problems aside and catch a killer.