After she had come to live in Palm Beach, Marion McKinlock’s life settled into a calm groove. She went to parties, gave the occasional interview, founded the Palm Beach Garden Club, lived in a lavish estate she called Casa Alejandro.

But until the healing factor of time came into play, the death of her son Alexander McKinlock Jr. in World War I was devastation personified. So devastating that it might help explain why she let a daffy grandaughter of John D. Rockefeller pretend to be married to her quite dead son.

This only-in-Palm-Beach tale is just one of the stories in “Five Lieutenants,” a new book by James Carl Nelson about five Harvard students from the classes of 1916 and 1917 who enlisted in the American Expeditionary Force in World War I. Some lived; some died; one had a nervous breakdown.

Cumulatively, the book is both social and military history, as well as a corrective to the common trait of dismissing America’s 18-month involvement in World War I as a minor inconvenience.

“I wondered about the experience of these rich kids at a time when hardly anybody went to college,” says Nelson. “Only about 2 percent of the population went to college at this time. Most of the AEF were farm boys and high school graduates, and I wanted to find out what was it like for these guys to be in that dynamic.”

George Alexander McKinlock Jr was raised in Lake Forest, Illinois by a domineering father and a mother who might fairly be called doting. His letters to her during the war are those of a unapologetic Momma’s Boy - patronizing to the Europeans, clearly basking in his status as the apple of his mother’s eye.

The father owned the Central Electric Company, a midwestern industrial behemoth, and the family had homes in Deer Isle, Maine, and Palm Beach as well as Lake Forest. Alexander made it into Harvard and onto the varsity football team; the high point of his college career was intercepting a pass against Carlisle in 1915 and running it back 80 yards for a touchdown.

“He was unformed,” says Nelson. “He was a guy who was drifting through life, waiting for something to happen. When he was in France, he was thinking that he might go into the artillery. On the cusp of his death, he had a cushy staff job, but he was thinking he might want to get a platoon or infantry company.

“I don’t know if callow is the right word, but I got a sense that the war was something he was going to do and then go home and take over the family business, which he was obviously being groomed for.”

Alexander McKinlock Jr. survived the battle of Cantigny, but then his luck ran out. He was walking down a road in France on July 21st, 1918, talking to a couple of French officers from a Moroccan division, when he was shot in the head. He was probably dead before he hit the ground.

Nobody knew who shot him, but what made it particularly interesting was that nobody was sure who dragged his body off the trail and nobody knew who buried him or where. For some time nobody was sure that he was in fact dead, or, if he was dead, where he was buried.

(Burial records in World War I weren’t much more advanced than they had been in the Civil War. A lot of men were buried where they fell without any marker whatever, and thousands were pulped in battlefield bombardments. To this day, bone fragments and occasional pieces of jewelry turn up in French and Belgian fields.)

Marion McKinlock was already involved in the war effort as the head of the Red Cross canteen in Chicago, but with her son MIA she sprang into action. “You can detect the privilege in her letters,” says Nelson. “There are letters to the sister of General John Pershing. She didn’t feel she could trust the little people, and she was right.”

Six months after the war was over, it was obvious that Alexander was dead, but Marion McKinlock still had no real idea where her boy was buried. And then came the event that makes you wonder.

In May, 1919, she went to France and found his grave in the garden of a home in a town called Berzy-le-Sec. Hanging on a little cross was the dead man’s helmet, and written on the cross was the name “McKinlow,” which the burial detail hadn’t noticed was awfully close to “McKinlock.”

“In the burial file, it’s presented as her walking right to the grave - some place the graves registration service hadn’t noticed. But then the files are full of ‘We can’t find this guy.’ They would exhume guys who turned out to be dead Germans.”

Marion Mckinlock had her son’s body reburied in a small cemetery. Still later she had him cremated and shipped home.

Alexander’s parents poured money into memorializing their boy - a half million dollars for a dormitory in his name at Harvard, more money for a campus for Northwestern in downtown Chicago.

Marion McKinlock and her husband had been coming to Palm Beach since 1914, and it was here that Muriel McCormick came into her life. Muriel was the granddaughter of both John D. Rockefeller and Cyrus McCormick. Her mother was interested in the psychic investigation that was all the rage; she had recently become convinced that she was the reincarnation of the first wife of King Tut.

Muriel attended a seance of her own, and was addressed by a spirit she believed to be the late Alexander McKinlock Jr., whom she had never met. The flirtation grew feverish. “The spirit’s lovemaking was said to have become increasingly passionate,” reported the Chicago Tribune with an admirably straight face, “and Miss McCormick became increasingly interested in her gallant spectre.”

Muriel McCormick met the McKinlock’s, moved into their house, and had a wedding ring fashioned out of platinum inlaid with black.

“I think half of it was high society goofing around,” says Nelson, “and half of it was real. Marian said that it was a testament to all the young men who died over there. I don’t know how much Marion embraced the spiritualist thing. It obviously helped her process her son’s death; I think it helped her grieving. She and McCormick became great friends and stayed great friends.”

This charade of barely repressed hysteria went on for a number of years until Muriel found that the dead are hard-pressed to give the comfort or pleasure that the living can. In 1931, she married a live man named Elisha Hubbard at the McKinlock estate.

The stock market crash hurt the McKinlock’s, but they maintained a Palm Beach residence for the rest of their lives. McKinlock senior died in 1936.

Marion McKinlock founded the Palm Beach Garden Club and also was one of the movers behind the formation of the Society of the Four Arts.

She lived in Palm Beach until her death in 1964. She was buried in Lake Forest, next to the ashes of her son Alexander.