Ten years after my grandfather's death, my aunt showed me a diary that had been found among his possessions. My astonishment was exceeded only by my joy. I begged to see it, promised to protect it with my life and brought it away with me. Here, I thought, was my chance to know him in a completely unexpected way.

The small green leather-bound book had been bought in London in November 1917. Lt. Cornelius T. McCarthy was one of 1,500 American reserve medical officers who volunteered in August 1917 to assist the Royal Army Medical Corps in France. He was 30 years old and unmarried.

A diary is an intimate document. The private thoughts set down by the author on a daily basis are rarely intended for a wide audience. To feel the thin, yellowing paper; to trace with one's eye the peculiar flow of the script; to hear with one's mind the sound of the author's voice is a powerful physical and emotional experience. How much more so in this instance to see the hear the words of a man who was silenced by a stroke long before I was old enough to ask the hard questions. I remember trying to understand him, but rarely could I make a pattern of the gasping sounds he managed with so much effort. I used to dream of miracles.

The first entry is dated 21 November 1917; the last, 20 February 1919, the day he sailed for home. With a thick-nibbed pen and blue-black ink, my grandfather left a record of 15 months of his life, 15 months of trench warfare that he had never spoken of to his family. No one had known of the diary while he was alive and apparently he had never felt inclined to tell his six daughters what it was like "over there."

There were long passages in shorthand. I had only to translate them! But for the longest time, I couldn't find anyone who could decipher it. I felt certain there were secrets to be found.

I had reached a dead end, or so I thought, until one day an English friend, who had learned shorthand in London, came to the rescue. My grandfather had used the Pitman method of notation, not the Gregg that is the one used in this country. The translator of the Rosetta Stone could not have been more elated than I as those idiosyncratic dots and dashes were transformed by my friend into recognizable shapes.

What emerged was a captivating profile of a man high-spirited, humorous and confident. And -- much to the surprise of the family -- quite a ladies' man!

He wrote each entry as if it were a telegram: short, staccato bursts of words that even in their simplicity manage to convey the texture of his thoughts through the years. "Thanksgiving Day 1917. Beautiful day at Hieudocourt. Do not expect turkey. Thankful that I am living. Awakened at 4 a.m. by terrific barrage. There is bloody murder going on in the Bourlon Wood."

In March 1918, he went to Paris for the first time. He dined at Maxim's . . . "where the pretty girls are seen. All golddiggers. You put your six-shooter on the table beside you as you order. 60F per. More if we didn't use persuasion." During the day, he took in the sights with Mlle. Elise.

In May of that year he was badly gassed during the last big German offensive on the Western Front. "Overtook D Co. Were caught in a barrage. Many men knocked out. Stopped by side road -- crawled into fields to bind them up. Left alone. Felt my time had come." He had taken off his gas mask to help the wounded. He was blind for a week. This was his ticket back to Blighty, but, incredibly enough, he wrote then ". . . wished I was up front line."

The summer of 1918 must have been idyllic after so many months in the trenches. From the entries during these months it is clear that he spent most of his time in the company of a Miss Alice Whitney of Boston. When the shorthand was translated, a romance took shape. Luncheons at the Savoy, nights at the theater, weekends at a country house in Kent -- an enviable way to recover one's health. Alice was with him in December at Buckingham Palace as he was p ersonally decorated by King George V. He was the first American to receive the British Military Cross. The last words in his diary are "Sailed on Aquitania for Home Sweet Home. Very sad to leave Alice. My love."

It was not the miracle I had prayed for, but this diary let me know my grandfather in a way he could never have anticipated. We even shared a secret -- for Alice did not become my grandmother.