Irish writer Lucy Costigan’s new book, “Glenveagh Mystery: The Life, Work, & Disappearance of Arthur Kingsley Porter,” has all the elements of a gothic mystery novel: a multimillionaire Harvard professor, a castle on a desolate island, and a salacious family drama. But the book, released Saturday, is in fact a historical account researched for over 10 years by Costigan and the Arthur Kingsley Porter Project team, a group dedicated to unearthing the truth behind his disappearance.

Porter was an art history professor with considerable academic renown. In 1929, he moved with his wife to Glenveagh Castle on a secluded island in Donegal, Ireland. Four years later, Porter disappeared without a trace while walking around his property. Was it murder? Was it an accident? Did he commit suicide? Or did Porter obtain a secret passage to Europe, where he lived under an assumed name?

These questions intrigued Costigan and her friend Thomas Williams, now project manager, after they visited Glenveagh Castle with Costigan’s nephew Michael Cullen, now project photographer. Williams persuaded Costigan, who had recently published the non-fiction book “Strangest Genius: The Stained Glass of Harry Clarke” about an Irish stained-glass artist, to write a book about the Porter mystery. The research team travelled to Stanford, Yale, Harvard, and Woodland Cemetery in Connecticut to research the story.

“There was a lot of intrigue that we discovered using [digitized historical] newspaper articles,” said project researcher Theresa Cullen regarding Porter’s early life. After Porter’s mother died when he was eight years old, his father began corresponding with at least a dozen young women including his son’s governess, which prompted his older sons to attempt to have him declared insane. Porter left his turbulent family when he matriculated at Yale, where a semi-spiritual experience in the Cathedral of Coutances in 1904 led him to cast aside his earlier ambitions of attending law school and instead devote himself to art history. He joined the Harvard faculty in 1920.

Porter had a presence at Harvard that has recently been scrutinized in light of changing norms. A 2002 Crimson article clued the team in to the University-organized “Secret Court” of 1920, which investigated students suspected of homosexual activity. “It was a time when absolutely everyone was being checked out, all the students and all the professors. Harvard wasn’t a great place to be in the 1920s,” Costigan said. “From the diaries, it seems that [then-President of Harvard Abbott Lawrence] Lowell took a certain interest in the lifestyle of Kingsley Porter and perhaps even went so far as to harass him by calling him to Lowell House all the time and questioning him,” she noted. “He certainly felt that it was time to leave.”

Porter’s academic record was also controversial; he was involved in transporting a sarcophagus lid from Spain to Harvard’s Fogg Museum. Immediately afterward, Porter began experiencing symptoms of depression. The move instigated serious debate between Harvard and the Spanish government, and the lid was finally returned on the day that Porter was last seen. “If someone wanted a supernatural explanation, it is there as well,” Costigan said.

Costigan has not made up her mind about what happened to Porter, but the investigation did uncover a new finding in the official police inquest, stored in the National Archives office in Dublin. “People have gone over the inquest before, but it’s all handwritten and hard to decipher,” Costigan said. “It had been assumed that no boat left the island…but in fact there was a [ferryman] that rode across on the day that Kingsley Porter was last seen…. If he had wanted anything, with his money and influence there’s no doubt he could have gotten it, including a passage from the island.”

Porter’s legacy is still visible at Harvard today in the various professorships that are named after him, including at the Dumbarton Oaks Research Library and the Philosophy Department. “Porter is admired today as a pioneer, someone who went out and did heroic field work,” said History of Art and Architecture professor Jeffrey F. Hamburger. Porter was noteworthy, according to Hamburger, for investigating artifacts from multiple nations of origin at a time when the study of art history was nationally segregated, with Spanish scholars studying Spanish architecture and French scholars concentrating on France. “When Porter [lived], to cover the monuments as assiduously as he did was really a heroic undertaking,” Hamburger said. “Today we can conjure up images ad infinitum on the internet, and it’s very easy to take that kind of documentary work for granted.”

Harvard currently possesses 35,000 of Porter’s photographs, taken throughout the professor’s travels, as well as the diaries of Porter’s wife, both of which are now housed in the Pusey Library. “There was actually a great love story in the relationship and the letters they wrote to each other, almost like soulmates for much of their marriage,” Costigan said. Lucy Porter was very involved in the research for her husband’s books, and after his disappearance she continued his work and even traveled to Europe on an archeological expedition.

The story of Porter is also being turned into a documentary and a feature film, produced by Donegal-based Lugh Films and expected to begin filming in 2013. The Arthur Kingsley Porter Project has bolstered the economy of Donegal, according to Williams: it has inspired increased tourism, a play about Porter’s life, portraits of the Porter family, a local art competition, original jewelry, music composed for harp, and a commemorative pen series designed by two Irish brothers, aged 13 and 14.

For Williams, the conclusion of his involvement with Porter’s story is a fulfilling moment. “It’s like Kingsley Porter has been directing me this whole time. He’s been on my case, and I’m ready for him to let me go after 10 years,” he said.

—Staff writer Ola Topczewska can be reached at atopczewska@college.harvard.edu.