plot masterminded by the Rev. Philip Berrigan, along with other current and former priests or nuns, to blow up tunnels beneath Washington, D.C., and then kidnap Henry Kissinger, President Richard Nixon's national security adviser, and hold him until the U.S. stopped bombing Southeast Asia.

Much of the evidence came from an informant who had been in prison with Berrigan and then got a job as a library assistant, where he prevailed on Ms. Horn, a tax-withholding opponent of the Vietnam War, to host a meeting with some of Berrigan's friends.

Her phone was tapped

During the legal proceedings, Ms. Horn learned that her phone had been wiretapped, said her daughter, Catherine Marrion. Prosecutors pressed Ms. Horn for information about the supposed plot. But after appearing before the grand jury, she refusedto testify at the 1972 trial of the so-called Harrisburg Seven and was led away in handcuffs. She was freed after 20 days when the jury deadlocked on the conspiracy charges, which were then dropped.

She was "the first librarian who spent time in jail for a value of our profession," said Judith Krug, director of the American Library Association's Office for Intellectual Freedom. The association declared during Ms. Horn's trial that it could not support her defiance, but praised her after her release, and later elected her to its governing board.

In the aftermath of the trial, Ms. Horn, who had moved to California, found that she could no longer get a top-level job at a public or college library.

"Because she was seen as controversial, I think they didn't