Holy Hour had just ended at St. Agnes Catholic Church in Arlington yesterday, and the Rev. Thomas VanderWoude was heading back to the office. "Is it a boy or a girl?" he heard the secretaries saying.

"I walk in, and they're all in tears holding a baby," VanderWoude said. "I thought they were talking about a cat, and they're holding a baby."

A McLean woman attending afternoon church services had just found the newborn baby, a little girl, in a bathroom in the church basement. The baby was swaddled in a T-shirt and lying in a basket.

Rescue workers soon arrived at the church on North Randolph Street, in the Cherrydale area, and VanderWoude could tell by the way they were talking that the baby was in distress. They were calling for a helicopter to get her to Arlington Hospital as quickly as possible.

Before they slipped an oxygen mask over her tiny face, however, VanderWoude quickly stepped in. "I went over and baptized her," VanderWoude said. "Right there on the desk."

The child was baptized Mary Agnes "for the Blessed Mother and Agnes, where the child was found," said the Rev. James R. Gould.

The oxygen seemed to work a miracle, and the helicopter was canceled. Mary Agnes was improving last night at Arlington Hospital and was admitted to the well-baby unit, a spokeswoman said.

Cpl. Justin McNaull, an Arlington police spokesman, said police believe that the baby, who was found after the service ended at 3 p.m., was born somewhere else and brought soon afterward to the church. "We're also concerned about the mom, for her safety," he said.

Church officials do not believe the baby had been at the church long. Veronica Weaver, 74, who found the infant, said she had been in the bathroom before the service started, about 1:45 p.m., and had not seen any baby.

On her way out, she stopped in again. The light was on, the toilet seat was up and behind it "there was this little basket with this little, little baby in it," Weaver said. "I thought it was a doll. I said, `It's a real baby!' And I touched its little toes."

The baby, who was very clean and had a tuft of brown hair, was sound asleep, and Weaver ran out of the room to get help. The child was brought to the rectory, and someone called 911. Except for a nasty bruise on her head, the baby seemed fine, Weaver said. "It was a beautiful baby."

Gould said there were no signs that the baby had been born in the church. About 50 or 60 people attended the service, but so far no one has recalled seeing anyone with a baby, he said.

Arlington police said last night that the brown-eyed, 20-inch-long, 7-pound 1-ounce baby is believed to have been born within 24 hours of being found in the church.

Gould urged the mother to come forward and praised her for her "courage and generosity" in carrying the child. "She probably didn't see it as enough," he said.

"God loved you in offering you that child, and God loves you in having that child, and God loves that child very much," Gould said in his appeal to the mother. "Call me at St. Agnes," he said. "But come home and allow your child to come home to you. We will do anything to help."

Gould said he comes from a family of orphans and that the discovery has "hit home very close here."

VanderWoude agreed, saying everyone at the church is "overjoyed that this woman gave this baby life."

"For some reason, she decided to put that baby here," VanderWoude said. "We're taking that as a clear sign to help this baby."