One spring night 85 years ago, a Harvard student named Cyril Wilcox lay in bed, breathing deeply. Gas flowed from an open jet in his room. By morning, he was dead.

Thanks to some incriminating letters, Wilcox’s older brother, Lester, thought he knew exactly whom to blame for the apparent suicide: a circle of homosexual Harvard students, who, he believed, had seduced his innocent brother into a life of debauchery and perversion.

Enlisting the help of the university’s president and high-ranking deans, Lester embarked on a remarkably successful crusade to expel Cyril’s gay classmates. The school set up a covert court to try dozens of students known to frequent drag parties in Harvard Yard. Seven undergraduates eventually were expelled, and the university continued to persecute some of them for the next several decades, informing other schools and potential employers – not to mention parents – of their alleged crimes.

The inquisition was conducted so stealthily on campus, though, that it was all but forgotten until The Harvard Crimson published an account of the scandal in 2002, a feisty piece of journalism that William Wright revisits and, to an extent, expands upon in his new book, “Harvard’s Secret Court: The Savage 1920 Purge of Campus Homosexuals” (St. Martin’s Press).

It’s hard to imagine a better opportunity for a history book. Thanks to Harvard’s huge and meticulous internal records collection, Wright – the Yale-educated author of “All the Pain that Money Can Buy: The Life of Christina Onassis,” and “Heiress: The Rich Life of Marjorie Merriweather Post” – had access to about 500 pages of primary documents detailing the court’s machinations, most of which occurred in the spring of 1920.

Because The Crimson had done much of the grunt work – fighting for the initial release of the papers, then cracking the code that hid the students’ identities – Wright could dive right into the treasure trove of sources: letters from the boys and their distraught mothers, meeting notes so precise that Wright was able to reconstruct dialogue. Also, because some of the students’ relatives are still alive, Wright could do some journalistic gumshoeing of his own. He found that most of the expelled boys went on to lead compellingly miserable lives; two of them committed suicide.

This is a story that stands on its own, only Wright lets his huffy exposition cheapen the tragedy. He can’t just list Harvard’s plentiful sins, then sit back and watch the university hang itself. Instead he scolds administrators for their “furious excesses” and the school for its “egregious” failures. The court is not only secret but “savage.”

And he doesn’t stop with Harvard, instead lashing out at the American culture that put it on a pedestal. He attacks everyone from a Navy machinist who, in 1917, carried out a homosexual sting operation in Newport, R.I., to the gay poet Walt Whitman, who was “craven and dishonest” for not outing himself in the late 1800s – an era when the concept of a gay identity barely existed.

Some of Wright’s commentary is inappropriate; all of it is unnecessary, because many 21st-century readers naturally would sympathize with the boys and recoil at the university’s callousness.

Wright’s anger is righteous and well-directed. But, on the page, it limits our ability to understand the court in its historical context, and distracts us from what is otherwise a thorough and readable account of a dark moment in American academia.