Even before the events for which she is best known, Grace Humiston was a pioneer. She graduated from Hunter College in her hometown of New York City in 1888 and from New York University Law School after its dean promoted her from the night school to the regular program. When she was admitted to the New York bar in 1905, Humiston was one of only 1,000 female lawyers in the country.

As Brad Ricca explains in "Mrs. Sherlock Holmes," a briskly paced true-crime tale, "the indomitable woman in black" gains a reputation as a dogged investigator and tireless defender of mistreated women. When a New Jersey woman is sentenced to death for murdering her town's richest man, Humiston gets the sentence commuted to 7½ years in prison — the first time in New Jersey history that the court of pardons had commuted a death sentence.

In 1907, Humiston investigates a peonage scheme in which Italian immigrants are taken to a Louisiana plantation where the workers are so "immobilized by debt" to the owners that they can't afford to leave.

These early cases set the scene for Humiston's most famous case. In 1917, 18-year-old Ruth Cruger left her parents' Harlem apartment to have her ice skates sharpened at Alfredo Cocchi's motorcycle shop. She didn't return.

What follows is a riveting account of Humiston's investigation. From the moment she becomes the Crugers' lawyer, the press dubs her "Mrs. Sherlock Holmes." And that is indeed the role she plays: conducting interviews, following leads, finagling ways to enter Cocchi's shop when his wife refuses to let her in. And Humiston succeeds where the New York Police Department and attorney general's office failed — embarrassments that, given the ethos of 1917, were even more humiliating coming from a woman.

Although the book is billed as Grace's story, she's a supporting player rather than the central figure. Ricca's focus is instead the Italian community in early 20th-century New York, the judicial system in Italy and the practice of white slavery.

“Mrs. Sherlock Holmes: The True Story of New York City’s Greatest Female Detective and the 1917 Missing Girl Case That Captivated a Nation,” by Brad Ricca

But "Mrs. Sherlock Holmes" is nonetheless a fascinating read. Ricca overdoes the old-timey prose — Captain Alonzo Cooper is "the pug-faced head of the Fourth Branch gumshoes"; police "cooled their heels" — but compensates with an engagingly novelistic style and perfect details, as when he describes the mechanical baptismal font that rises from a secret underground chamber in the church where Ruth Cruger read to children.

Late in the book, when asked about her nickname, Humiston says, "I am not a believer in deduction. Common sense and persistence will always solve a mystery." Arthur Conan Doyle's creation may have preferred more theatricality, but he would have approved of Humiston's results.

Michael Magras is a member of the National Book Critics Circle. His work has appeared in the Houston Chronicle, Philadelphia Inquirer, San Francisco Chronicle and Pittsburgh Post-Gazette.

Mrs. Sherlock Holmes
By: Brad Ricca.
Publisher: St. Martin's Press, 436 pages, $27.99.