Rating: FRC-ish (brief and non-graphical mentions of violence and sexual relations involving very-nearly-18yr old, that do not nearly justify FRT)
Notes: many thanks to bessemerprocess, who beta'ed; tanyad, for her help with everything Chicago; and tamara_russo, who spent many hours developing this story with me. Story title from the classical Chaos Theory paper. (TY Li & JA Yorke (1975) Period Three Implies Chaos. American Mathematical Monthly 82:985–992.)
Summary: Chicago, December 2010. When Kyle Woods, 17, goes missing in Chicago, the suspects are his girlfriend, Vikki, and a 21-year-old with a record, Jay. With snow piling up in the streets and Jay and Vikki refusing to talk, the BAU are called in to find Kyle before it is too late.
AO3 | DW | LJ