Hilary Russell and her parents, Susan and Richard, were on a mission of mercy that blustery winter day in 1978 as they drove from their Miami home to the deserted stretch of Miami Beach. Their English springer spaniel Siddhartha had a bad case of fleas. "We had tried powders and baths but nothing worked," says Susan. "So we asked people, and they said we should take him to the beach and get him in the salt water."

But before Richard, a poet and English professor, and Susan, a photographer and onetime lifeguard, could unpack their blankets, Hilary, then six and an enthusiastic swimmer, made a beeline for the roiling surf and waded into trouble. Her parents yelled at her to come in, but it was too late. Hilary was caught in a riptide. "There was nothing I could do," says Susan, now 58. "I couldn't make any headway. I wasn't strong enough. I thought, This child is going to drown because we can't get to her. There was no one else around."

She was wrong. Richard suddenly noticed a dark-haired man of about 30 standing about eight feet beyond Hilary. When the stranger saw she was in trouble, Richard says, he "just plucked her out of the water and held her in his arms."

Hilary, now 25, remembers little of her savior. "He was tan," she says, "and the hair on his arms was dark, and it glistened even though it was cloudy out." What astonished Susan was the effortless way the man strode through the waves, which reached only to his chest, although he seemed to be in deeper.

Back on shore, the man put Hilary in Susan's arms. "I said, 'Thank you. Thank God,'" recalls Susan. Adds Richard: "I remember him saying, 'That's okay,' and he was smiling." The Russells then embraced—but when they looked back, the man was gone.

Back home, Susan named him Hilary's Angel. Later, she says, "It occurred to me that maybe he really was an angel." Richard is convinced of it. As for Hilary, "I'm not real sure if there are higher powers," says the University of North Carolina junior, "but I think things happen for a reason, and there's a reason I was saved that day. It wasn't my time to go, I guess."