Robert Redford’s latest film, The Conspirator — released just days after the Sesquicentennial of the attack on Fort Sumter, the Civil War’s start — stirred many childhood memories.

My great-grandmother, Lillian Webster Keane, who was a longtime Washingtonian, frequently spoke about the injustice the film portrays.

Fittingly, The Conspirator opened April 15 — the same day, 146 years earlier, President Abraham Lincoln was celebrating the end of the Civil War.

The bloody conflict that ripped our nation apart for four years, North against South, was now over — ending officially on April 9, 1865, when Confederate Gen. Robert E. Lee surrendered at Appomattox Courthouse to Union Gen. Ulysses S. Grant.

After enjoying a pleasant carriage ride with first lady Mary Todd Lincoln, soaking in springtime Washington, this president, a lover of literature, was soaking in Our American Cousin at his box in the new Ford’s Theatre.

Of course, drama of an epic nature would soon envelop the audience, when Confederate sympathizer John Wilkes Booth, a well-known actor and familiar face at the theater, slipped into Lincoln’s box and fatally shot him, yelling, “Sic semper tyrannus” (thus always to tyrants), as he plunged onto the stage and injured his leg, limping to his well-planned escape.

In the ensuing investigation into the tragedy, Mary Surratt, a Maryland Catholic, was accused and convicted of conspiring to kill the president. She was executed by hanging on July 7, 1865. She is played by Robin Wright in Redford’s film.

Lillian Webster knew Father Jacob Walter, who was close to Surratt. (In fact, he heard Surratt’s last confession before she was executed.) Lillian said Father Walter always contended, “They hung an innocent woman.”

Ironically, Lincoln foreshadowed this injustice.

As he wrote to close friend Joshua Speed 10 years earlier, “As a nation, we began by declaring that ‘All men are created equal.’ When the Know-Nothings get control, it will read ‘All men are created equal, except Negroes and foreigners and Catholics.’ When it comes to this, I shall prefer emigrating to some country where they make no pretense of loving liberty — to Russia, for instance, where despotism can be taken pure, and without the base alloy of hypocrisy.”

My great-grandmother’s father, Bradshaw Hall Webster, had worked on Lincoln’s presidential campaign fresh out of college. In the course of campaigning, this son of the North met my great-great-grandmother, Martha Mungen Starrett, whose family owned a plantation in Jacksonville, Fla.

When Bradshaw’s lumber mill in Orono, Maine, burned down, he took up the cause of temperance, as a “writer and orator,” traveling up and down the Eastern seaboard. After Martha died in 1881, the 33rd-degree Mason remarried — of all things, a Catholic, whom he met through the convent school his daughters attended.

Lillian, born in 1878, was only 3 at the time of her father’s remarriage, and she soon became a Catholic. She noted in her diary how the faith “lightened the burdens of life.” In 1888, after President Benjamin Harrison’s election, Bradshaw moved his family to Washington.

So it is that my “blue blood” great-grandmother, related to Daniel Webster and President William Henry Harrison, grew up in a social and cultural milieu in which the Civil War conflict still burned brightly so many years later.

She mingled with Washington’s Catholic community, which included friends of the wrongfully accused and executed Southern sympathizer Mary Surratt, and dated the son of Dr. Samuel Mudd, the doctor who set Booth’s broken leg.

After Lincoln’s assassination, the desire for retribution was so intense, a kangaroo military tribunal, portrayed in The Conspirator, sent Surratt to her death — a fate she faced with faith, clinging to her constantly held rosary beads and praying until the end.

As my great-grandmother always wisely counseled, “Two wrongs don’t make a right.”

Her daughter, my grandmother Helena, like Surratt, died much too young — the victim not of injustice, but of a heart weakened by rheumatic fever that just stopped one day, on the way home from grandma’s, as she held my mother, then 6 months old, in her arms.

Like Dr. Mudd, whose ancestors have tried in vain posthumously to overturn his conviction — though President Andrew Johnson pardoned him in 1869 largely because of his work saving yellow-fever victims at his military prison, as portrayed in The Prisoner of Shark Island (1936) — Mary Surratt’s name is still mud — something The Conspirator will hopefully help correct.

Thus would she finally rest in peace right there in Mount Olivet Cemetery in Northeast Washington, not far from where my grandmother Helena is buried.

Mary Claire Kendall is a Washington-based journalist and screenwriter.