The truth came out at a family Christmas dinner in 1990. Her mother looked across the table at one of Guyver's sons, then 18, and made a startling observation: He looked just like an American GI she had known in 1944 . . . just like Guyver's father.

The revelation changed Guyver's life.

For nearly two decades since then, she has been searching for her father, David Greene, a Pennsylvania man who was stationed at an Army Air Corps base in Chelveston, Northamptonshire, in the fall of 1944.

She has spent thousands of British pounds, filled up nine two-drawer filing cabinets with correspondence, and traveled to the United States, even knocking on doors in Philadelphia as she tried to find him.

Today, Father's Day, is emotional for her. Time is running out. Every day that passes makes her long-anticipated reunion less likely.

"Half of me is missing," said the 63-year-old clinical psychologist. "I don't feel a complete person."

Guyver is one of tens of thousands of children across Europe and the Pacific who were fathered by American GIs during World War II.

They are in England, France, Belgium, the Netherlands, Australia, New Zealand, Germany, and elsewhere.

The sons and daughters are in their 60s and the fathers in their 80s or 90s, giving the search a now-or-never urgency.

"I would like to know what he did with his life," Guyver said. "Where did his family come from? I did my family tree to 1295 on my mother's side, and I went back to 1442 on my husband's side. But I can't do anything on my father's side."

Guyver said her mother and father had met a few times at dances in Chelveston in October and November 1944 while he served as an Army dispatch rider, probably in a support unit of the 305th Bombardment Group of the Eighth Air Force. She served in Britain's Women's Auxiliary Air Force.

"He told my mother he had been in the police force before," Guyver said. "It might have been in Philadelphia or Pittsburgh. He said he went out on a domestic call one time and was hit over the head with a frying pan. My mother thought that was quite good."

People from many backgrounds were thrown together during the war and struck up quick friendships. Guyver's mother used to see Greene riding his motorbike around the air base. He was a striking GI, standing 6 feet tall, weighing about 160 pounds, with an athletic build.

"During World War II, life was so different in Great Britain. . . . You could be bombed at any time and be gone," Guyver said. "You could be dead just like that. You lived for the moment."

Guyver's mother became pregnant, gave birth, tried unsuccessfully to find the GI, and ended up marrying a member of the British navy. Even now, the 87-year-old - whose identity was withheld by her daughter - keeps her GI secret, not wishing to carry the stigma of giving birth to a "war babe."

"She just wanted to forget him. She doesn't know if he survived the war," Guyver said. If he's living, "my father doesn't know he has a daughter, two grandsons, and four great-grandchildren."

Some of the GI children have joined support organizations such as Transatlantic Childrens' Enterprise, known as TRACE (www.tracepw.org/), a British group founded by a GI war bride, and www.gitrace.org, which offers tips for finding fathers and useful online links.

The music of "Somewhere Out There" plays over the gitrace Web site, and poems express the feelings of those still looking for their fathers. One, by Janette Taylor, reads in part:

I've longed to know my father