Rebecca Davis

It's early in the morning and 20-year-old Aaron Reid looks like he's sleepwalking.

His head nods forward and he shuffles a bit as he heads toward the pediatric clinic at the National Institutes of Health Clinical Center.

Reid, who has been fighting leukemia since he was 9-years old, is experiencing intense pain.

He can't say much at the moment, so his mother, Tracie Glascox, speaks for him. "He's been complaining of pain in his ankles, his knees and his arms," she tells the nurse.

OK, so you've just left the hospital with your newborn baby. You're relieved, because the baby is healthy, your heart overflows with love and you're excited to begin this new chapter in your life. Then, most parents will tell you, on the way home a strange feeling sets in.

It's as if you went to sleep in one world and woke up in another, a world that seems familiar but slightly off-key. As you gaze into the eyes of this fragile new being, it hits you: "What have I done?" And, more importantly, "What do I do now?"

Editor's note: This story contains language that may be offensive.

In February 2009, Samantha Pierce became pregnant with twins. It was a time when things were going really well in her life.

She and her husband had recently gotten married. They had good jobs.

"I was a kick-ass community organizer," says Pierce, who is African-American and lives in Cleveland. She worked for a nonprofit that fought against predatory lending. The organization was growing, and Pierce had been promoted to management.

When Boyd Coble heard the sheriff's deputy pounding on his door in Houston in the middle of the night, he rolled over and went back to sleep. Coble, who lives alone, except for his Australian sheepdog, Wally, knew all about Hurricane Harvey. He just didn't think his own home would flood. It never had before, and even if a little water did trickle in, Coble was pretty sure he and Wally could ride it out.

German scientist Matthias Schmidt wants to extract rare earth metals from abandoned mines using bacteria. He has an unlikely partner — Nedal Said, a Syrian refugee scientist who escaped Aleppo.

Sharon Belvin's nightmare with cancer began in 2004, when she was just 22.

Belvin was an avid runner but said she suddenly found she couldn't climb the stairs without "a lot of difficulty breathing."

Eventually, after months of fruitless treatments for lung ailments like bronchitis, she was diagnosed with melanoma — a very serious skin cancer. It had already spread to her lungs, and the prognosis was grim. She had about a 50-50 chance of surviving the next six months.

"Yeah, that was the turning point of life, right there," she says.

A novel immunotherapy drug is credited for successfully treating former President Jimmy Carter's advanced melanoma. Instead of killing cancer cells, these drugs boost the patient's immune system, which does the job instead.

Immunotherapy is cutting-edge cancer treatment, but the idea dates back more than 100 years, to a young surgeon who was willing to think outside the box.

This is the story of a man whose ideas could have saved a lot of lives and spared countless numbers of women and newborns' feverish and agonizing deaths.

You'll notice I said "could have."

The year was 1846, and our would-be hero was a Hungarian doctor named Ignaz Semmelweis.