Deadly Disguise — Cherie O'Boyle

...bodies falling... Estela Nogales is caught in the middle when the perfect murder sets off chaos during final exams week. Together with Detective Muñoz, who is stymied by the lack of evidence and witnesses scattering for the summer, Estela must use her acute powers of observation to help identify the killer. One calamity after another disrupts the investigation, and Estela is pursued at every turn by the mysterious figure in the hat, even home to Arroyo Loco where a fresh set of crises are unleashed.