For two days, Inna A. Belyantseva and her mother-in-law had clung together, in and out of fitful sleep, as they tried to stay calm and "keep hope" in a Moscow theater held hostage by armed Chechen rebels.

In Gaithersburg, Pavel Belyantsev and his 16-year-old daughter clung together, too. Every time the phone rang, they grabbed desperately for news. About his wife, a doctor and scientist at the National Institutes of Health who had been visiting relatives in Russia after a business trip in Europe, and his mother. A ticket to the popular musical "Nord-Ost" had been Belyantseva's 40th birthday treat.

The siege began Wednesday evening when the rebels stormed the crowded theater. Saturday morning, Russian special forces pumped gas into the ventilation system and mounted a counterassault. Fourteen hours later, Belyantseva awoke in a bed at Moscow City Veteran Hospital #1, groggy but otherwise unharmed. Her mother-in-law, Inna M. Belyantseva, was gone from her side.

Not until Sunday did she reach her husband by phone.

"She said she loved me," the software engineer recounted slowly yesterday. "I loved her. She was worried about my mother. . . . We were very, very happy when she called and she talked to us."

Then the phone rang one more time. Friends and relatives in Moscow had found his mother. She was in a city morgue, one of the 117 hostages to die.

"They said she never woke up," he said.

According to Belyantsev, his wife heard no gunshots, no scuffling and no screams when the government raid began. After nearly 58 hours being barricaded in their red, upholstered seats, she and her mother-in-law had been drifting in and out of fitful sleep. They never even saw the gray smoke wisping through the theater.

Belyantseva had intended to return to the United States on Oct. 21 but was delayed by visa problems. She and her family have lived in the United States since 1997, when she took a fellowship at the National Institute on Deafness and Other Communication Disorders. She has been promoted twice since and holds the title of senior research fellow.

"She's a highly skilled expert . . . in the field of of hearing research," said Bechara Kachar, a former supervisor who is chief of the cellular biology laboratory. "She's a wonderful person, a hard worker and a good friend. That's why we tried to keep her with all these promotions."

Belyantsev spoke to his wife Oct. 22, when he called to wish her happy birthday. He knew she planned on seeing the musical at the House of Culture for the State Ball-Bearing Factory -- the theater's name from Soviet days. He just didn't know which night she would go.

When she failed to answer the phone 10 hours later, he feared the worst. Friends stopped by Belyantsev's mother's apartment and found it shuttered and dark.

"So there is no place where they can be," he said. "They can only be at the theater."

His agonizing vigil began.

For him and Polina, a student at Thomas S. Wootton High School in Rockville, news that many hostages had died from the gas only made the wait more difficult. Friends and relatives in Moscow helped Belyantsev call hospitals there, but the lines either were busy or the officials who picked up said they could give out no information.

The first word that his wife was alive came from one of those friends. Belyantseva, unable to get through to the United States, had called the friend to relay the message.

Belyantsev talked with his wife again yesterday and said she is tired but doing well. They have not spoken much about her experiences inside the theater. "I'm afraid to ask," he said. "It's very hard for her. Maybe in the future."

She told him only that she and his mother were on the second floor. They stayed together the whole time, each trying to calm the other and to "keep hope," he said. He expects her back in the United States by next week.

The past week has been a draining seesaw of apprehension, fear, relief and sadness. His mother was 59.

"It's very hard," Belyantsev said. "But I'm very glad my wife is alive."

Russian police forces stand outside the theater where Chechen rebels held hundreds hostage late last week.Gaithersburg scientist Inna A. Belyantseva, 40, was one of the hostages who survived the takeover of the Moscow theater by Chechen rebels.