Constitucion, Chile (CNN) -- Cristina Perez furrows her brow, concentrating and trying not to let her gaze wander too wildly.
Alongside her, friend Marta Moya bows her head a little to disguise that she sometimes has trouble controlling her facial expressions.
Life has clearly dealt them a cruel hand. Both now in their 50s, they've been in care homes, or "asylums" as they still call them in Chile, since their late teens.
Perez has a mental disability and Moya is schizophrenic and epileptic.
Yet when an earthquake-spawned tsunami crashed into their care home on February 27 hours before dawn, both refused to drown and die without a fight. And with selfless loyalty, they refused to let their friends -- older and more frail than themselves -- perish, either.
Perez says she was knocked out of bed by the 8.8-magnitude quake around 3.30 a.m. Minutes later, she was trying to fathom why waves were crashing down the corridors of the care home, dragging away furniture, blowing out doors and walls and engulfing her friends up to their necks.
"I got desperate and thought, 'What can I do?' Nobody was coming, and I shouted and asked for help," Perez said.
"I thought we're going to drown here there's no way out. And none of us know how to swim."
The home, a few hundred yards from the Pacific Ocean and two blocks from the River Maule, is run by Catholic nuns. Two were on duty that night.
In charge was Sister Celinda Briso, fit, able and in her 30s. She fled to the relative safety of a second floor annex -- leaving 27 patients, mentally disabled, bedridden or in wheelchairs, to the mercy of the water.
"Many of them were crying and calling for help, but I couldn't do anything. I went upstairs and knelt and prayed. I was desperate. I blocked my ears," Briso explained.
Giving in was never an option for Perez. Her logic was simple.
"I only thought about my friends. I didn't want them to drown," she said, swallowing hard in an effort not to cry.
"I'm pretty agile so I ran. I was gripping onto the doors and the walls and made my way up the corridor. The other ladies had water up to their necks," she said.
"One door was jammed so I pushed it in. I took one lady by the hand. My friend Marta took her other hand, and we brought her out bit by bit. We did the same with some of the other ladies," Perez recounted.
At that point Moya took up the tale.
"I helped more than five old people. A wall fell down and almost crushed one. And there was another one in her 90s. I helped her too," Moya said, ending her sentence with a hearty laugh, part glee, part nerves.
Within earshot are a group of elderly ladies -- Priscilla, Laurentina, Eliana, Maria and a fifth who suffers from senile dementia and can't really remember what her name is.
All nod reverently at Perez and Moya. They owe their lives to them.
"The water was flowing really strong -- I couldn't get out. The water came right up to my neck," said 80-year-old Maria Gutierrez, gesturing. "I was shouting, 'Help me, I'm drowning.'"
Out in the sunny courtyard of a public school-turned-temporary shelter in Constitucion, Perez and Moya wonder if their minds may be playing tricks on them. They say the events of that morning seem so unreal.
But drive the couple of miles into town and back to the care home, and reality is there. It's wrecked.
The tsunami smashed the front door of the care home and toppled brick walls, bringing part of the roof with it. Inches of thick sludge coat the corridors and there's a tidemark about 1.5 meters, almost 5.5 feet up the walls.
Most of the furniture has been suctioned to the back of the building or into the rear yard.
In the chapel, a small wooden pew is upturned and a white statuette of the Virgin Mary lies face down, congealed in sludge and surrounded by silvery sardines.
After inspecting the damage at the care home, it was clear the horror of what residents went through that morning was worse than Moya and Perez were letting on.
According to many witnesses in Constitucion, three tsunami waves crashed ashore in quick succession within a few minutes of the 3.30 a.m. quake.
Briso said she and her fellow nun finally ventured back down to the ground floor of the care home to check on the patients around 7.30 or 8 a.m.
Perez and Moya had been unable to make it out of the corridors with the elderly ladies they'd rescued. And so they stood for hours -- until day began to break and the waters subsided -- holding hands to make sure none were dragged away.
"When it began to get light, one of the sisters came down. And we were all holding hands, and I shouted to her, 'Here they all are, they're all together,'" Cristina said.
Two patients, men in their 70s, died in the tsunami. Carlos Silva drowned when his bed turned over. Ernesto Valdes could have made it out but lagged behind to get dressed rather than running out wrapped in a blanket, Briso said.
But of the 27 men and women in the care home, 25 survived.
"I cried. I didn't want any of them to die, but I have to accept the will of God," Briso said, adding that she thought it was a "miracle" so many of the patients made it out alive.
But five frail ladies, who now have time to enjoy a little sunshine, have a more earthly explanation.
They survived because two loyal friends -- Moya and Perez -- found extraordinary strength and courage and simply refused to let them die.
When CNN visited the other care home survivors at their temporary shelter Tuesday, Moya and Perez sat knitting scarves. Moya's is yellow and Perez's is blue. They hope to be finished in about a week.
Chileans have been moved by the plight of the citizens of Constitucion, and Perez and company have received some donated clothes.
The trousers hang a little loose and the blouses and sweaters are a little baggy. But they're clean for the first time in 10 days. Perez says they even managed a full shower for the first time since the tsunami.
"It was even a little bit warm. Now I feel much, much better," she said.
But Gutierrez, one of the five Moya and Perez rescued, is feeling a little under the weather. She lost her clock-radio in the tsunami -- it was a constant companion on her bedside table. Bravely, she says she expects she'll make do without.
Meanwhile, Moya says she hopes her father, whom she's not seen in years, may come and take her for a short holiday.
Perez doesn't know anybody else outside the care home. Anyway, she's too busy for vacations.
"I'm needed here," she grins impishly. "In case I have to deal with any more emergencies."