In 1959, a grisly quadruple murder shook the rural community of Holcomb, Kansas. A wealthy farmer named Herbert Clutter was found murdered inside his home along with his wife and two teenage children—and the killers were still at large. The mysterious crime inspired author Truman Capote to write his seminal true-crime novel, In Cold Blood (1966). Turns out, it also unleashed the creative juices of his close friend, novelist Harper Lee.

According to The Guardian, biographer Charles J. Shields says he has discovered that Lee wrote a previously unknown feature magazine article about the Holcomb murders. The article has no byline; it originally ran in Grapevine, a magazine for FBI employees, in March 1960. Four months later, Lee published her Pulitzer Prize-winning work, To Kill a Mockingbird.

Capote traveled to Kansas on assignment for The New Yorker, where he interviewed police officials, townspeople, and friends and family of the deceased. Over time, the lengthy magazine story blossomed into a full-length book. Lee accompanied Capote, and assisted him in his reporting; Capote later referred to her as his “research assistant.” 

Turns out, Lee may have been far more involved with the project than Capote led on. While reading old Kansas newspapers for mentions of Lee, Shields found a column written by her friend, a woman named Dolores Hope, in the Garden City Telegram. A revealing paragraph caught his eye:

The story of the work of the FBI in general and KBI Agent Al Dewey in particular on the Clutter murders will appear in Grapevine, the FBI’s publication.

Nelle Harper Lee, young writer who came to Garden City with Truman Capote to gather material for a New Yorker magazine article on the Clutter case, wrote the piece. Miss Harper’s first novel is due for publication … this spring and advance reports say it is bound to be a success.

Shields contacted Grapevine, and staff members confirmed rumors of a Lee submission. However, they had never seen her byline. The vigilant biographer suggested they check their February or March issue from 1960. Sure enough, the March issue contained a feature story about the Clutter murders, including an interview with the Kansas Bureau of Investigation detective investigating the case.

“I speculate that there was no byline because she really didn’t want to tread on Truman Capote’s story,” Shields told The New York Times. “It’s a long flattering article about the great work chief investigator Alvin Dewey is doing on the case and how Truman is going to get to the bottom of it. It was an unselfish act from a friend.”

Shields included this new finding in an updated version of his 2006 biography, Mockingbird: A Portrait of Harper Lee. Grapevine will reprint Lee’s article next month, accompanied by an introduction written by Shields.

[h/t The Guardian]