In 1972, the I.R.A. abducted and “disappeared” Jean McConville, the mother of ten children, most of whom were teen-age or younger. Her case became one of the most notorious unsolved murders of the long period of unrest in Northern Ireland known as the Troubles. Patrick Radden Keefe wrote about McConville for The New Yorker in 2015. “On the one hand, it’s a story about a terrible murder that happened in 1972,” Keefe tells David Remnick. “On the other hand, it’s about how that history, far from being remote . . . was incredibly politically explosive.”

While researching a book about the murder, Keefe stumbled across an overlooked clue. Now, Keefe tells Remnick, he’s pretty sure he knows who murdered McConville.

Keefe’s book, “Say Nothing,” is available on February 26th.