“Someone who thought I knew I was getting a kidney asked, ‘You don’t know who your donor is?’ ” recalled Allen, an engineering contractor working on NASA’s Restore-L mission, which will endeavor to launch a robotic spacecraft in 2020 to refuel a live satellite.

For Allen, who had languished for four years on a national organ transplant list, this was an incredible revelation. But she was mystified as to who the person could be.

Allen’s husband, Rex, was the first to undergo living donor testing two years ago, but was excluded. Other relatives and friends who came forward were also rejected for various reasons.

With 95,000 of the 113,000 people currently registered with a national transplantation network waiting for a kidney, according to the Department of Health and Human Services, Allen could feel time slipping away from her.

Meanwhile, Jeannette Kendall had gone through the rigorous testing process without telling her close friend and Turf Valley neighbor.

Kendall, 60, is founder and executive director of Success in Style, a nonprofit that provides business attire and coaching to disadvantaged individuals seeking employment with profits from its four apparel resale shops in historic Savage Mill.

Kendall learned she’d been approved as a donor about the same time news of the transplant was leaked to Allen, but she couldn’t break away from work to deliver the news in person. She also has a busy personal life as a mother of nine.

Two weeks later, on Nov. 12, Kendall texted her friend that she and her husband would like to stop by, arousing Allen’s suspicions.

Allen still becomes emotional when she recounts the visit that changed her life.

“I open the door and there’s Jeannette and Paul Kendall with flowers and champagne,” Allen said, her body shaking. “I was so totally overwhelmed that Jeannette would do this for me.”

Kendall said donating a kidney in April was one of the best things to happen — to her.

“People don’t realize the donor is getting a great gift, too,” Kendall said. “Knowing I would be the one to save Hollys’s life …” she began, her voice trailing off, “was one of the best gifts I’ve ever gotten.”

Allen got the good news from Kendall just months after friends threw her a party at Bippy’s Pub on Route 40 to rally community support.

Everyone wore matching bright green T-shirts with white lettering that read, “Help Hollys Find A Kidney” on the front, and had blood type O and a phone number on the back. They also created a Facebook page to spread the word.

Even though Kendall was already deep into the testing process, she attended the party so people wouldn’t wonder why she didn’t show up.

But further testing soon revealed what seemed like a deal-breaker: Kendall’s blood doesn’t contain antibodies that Allen’s does, so Allen’s blood would attack Kendall’s kidney if she donated it.

Fortunately, that wasn’t the end of the road.

Doctors at the Johns Hopkins Comprehensive Transplant Center in Baltimore recommended Kendall consider paired kidney exchange, also known as “kidney swap.”

In this anonymous arrangement, living donors agree to swap kidneys so their intended recipients get organs that are more compatible. In some cases, there’s a long chain of donor-recipient pairs.

While Hopkins has participated in exchanges since 2001, Allen said the program opened up a whole new world for her and she wants more people to know about it.

“I would tell anybody who’s trying to find a living kidney donor — with T-shirts or Facebook pages — that paired exchange means blood type doesn’t have to be a factor,” she said.

One month after their champagne toast in November, Allen and Kendall got word the transplant coordinator had gotten “a hit” on a compatible donor-recipient pair.

“Finding a paired kidney exchange can take years, so we were incredibly fortunate,” Allen said.

Originally set for Jan. 15, the four procedures were postponed to April 9 while Kendall recovered from a health issue.

Kendall underwent surgery at Johns Hopkins to donate her kidney to the transplant patient waiting in Richmond, Virginia, while the donor known only to the patient and medical team in Richmond had surgery in Virginia to donate a kidney to Allen.

The kidneys were rushed by ambulances traveling in opposite directions and transplant surgery was successfully done on both recipients later the same day.

Rex Allen said he remains overwhelmed with gratitude.

“When I couldn’t be the one to save my wife, that was quite a setback,” said the retired construction superintendent. “Now, it’s like a light switch has been turned on in our lives.”

Paul Kendall, an attorney, described what he’d felt on the day of the surgeries, which lasted about four hours apiece.

“It was a remarkably profound experience for all of us,” he said, before getting choked up. “Every single action we take as human beings has a ripple effect … and that good can be the salvation of the world.”

Jeannette Kendall said she had resolved not to tell too many people she had donated a kidney, preferring to avoid the limelight. But a comment Allen’s daughter made on social media changed her mind.

“Willow wrote that she is once again looking forward to walking down the aisle and having her mother see her grandchildren someday, and that was further than her brain had gone in a long time,” Kendall said.

“That’s when I decided I needed to be more public about kidney donation so I might inspire somebody else,” she said. “How many times do you get the opportunity to save someone’s life?”

Kendall spent three days in the hospital after the surgery and worked at home for a month. After six weeks, she felt like herself again.

Allen quickly regained the color in her face after being white as chalk and soon felt like she and Frank – her name for her new kidney — could “get out and start running down the road.”

As tempting as that idea was, common sense prevailed. Allen is taking 11 prescriptions totaling 26 pills each day, though that number will gradually decrease. She is working at home and looking forward to returning to the office in July.

“Before the surgery, I was really focused on the present because I believed today might be all I had,” Allen said, her words clogged with emotion. “But thanks to Jeannette’s selfless act, I have hope. She is my superhero.”