In January 2022, investigative journalists Christy Gutowski and Stacy St. Clair got a phone call they weren't expecting. Their source had an intriguing tip about an unsolved mass murder. Back in 1982, someone put poison on store shelves across the Chicago area. People died at random, sparking a nationwide manhunt and an international panic. Investigators figured out what killed the victims. But the question of who killed them wouldn't be so quick to answer. The FBI spent four decades in a game of cat-and-mouse with one top suspect. But was he the killer? Or could it have been someone else? In Unsealed: The Tylenol Murders, the Chicago Tribune uncovers an active law enforcement investigation into a decades-old case — what may be the last chance to solve it.