THE SKY IS FIERCELY BLACK OVER THE ATLANTIC. I rest my head against the airplane pillow and let my eyes close.

When my sister, Betsy, Skyped me from Germany the day before, she was crying so hard that I couldn’t understand her. I caught “fluid in my abdomen” and “cancer marker.” She managed to explain that, after six punishing rounds of chemotherapy, there were still some signs that concerned the oncologist. She had a CT scan scheduled for Monday.

“I can’t take one more thing being wrong with me,” Betsy said, her gaunt face pixelated on my screen.

And I couldn’t take not being with my only sibling—who, at 52 years old, was fighting for her life. After the call, I booked my flight.

When I can’t sleep, I check the interactive flight map on my seat-back TV. We still have a lot of ocean to cross.

Seven months earlier I took this same flight to be with my sister when she underwent a partial hysterectomy. The follow-up labs revealed ovarian cancer. Three weeks after that I flew back for the next surgery, when they found a small metastasis in her diaphragm.

“You’re going to be okay,” I promised Betsy as I settled myself on the edge of the hospital bed on that second visit. She nodded and bit her lip. She was in a tiny triple room with two other cancer patients. If they all sat up and extended their arms they could almost hold hands.

I quietly wished that she were in a Boston facility and not the Klinikum Grosshadern, a barracks-style hospital. It’s not that I didn’t trust the German health care system; in fact, it has an excellent reputation. The problem was that I wanted to help Betsy through every appointment, but there was an ocean between us. And when I did visit, I couldn’t understand anything. Not the language. Not the hospital etiquette. And certainly not the missing niceties that one takes for granted in the United States.

“Why don’t they have privacy curtains between the beds?” I whispered to my sister as her roommates slept.

“Curtains aren’t sanitary,” she explained. “They can carry bacteria.”

I arrive in Germany, and after the CT scan on Monday morning, my sister and I wait impatiently for two hours. Finally an impassive clinician presents the results from across a large, sterile room. He refuses to look my sister in the eye, or speak in English for me.

“What the hell did he just say?” I ask Betsy after he leaves.

She rubs her hand over her bald head and exhales frustration. “I need more tests,” she explains.

The woman at the front desk offers her an appointment on Thursday—when Betsy is supposed to be leaving on a vacation. I can see disappointment in the droop of her thin shoulders. She had been looking forward to getting away from the hospital and her sickness.

“I’ll probably have to cancel the trip,” she says.

I spring into action. Betsy is a social worker who tends to listen politely to people without challenging them—an attitude that has allowed her to thrive in rule-abiding Germany for 18 years. I am not so patient and urge her to make a fuss.

“I guess I can call my gynecologist,” Betsy says. “Maybe she knows someone who can get my appointment changed.”

“Call her,” I say. “Now!”

I wish I could do this more—fight for her, and bring out her fighting spirit, as I did when we were children. And I, in turn, loved what being with her did for me, filling me with a kindness and sense of purpose that has come through our connection.

Our coordinated, Yankee push does the trick. My sister and her husband go to another hospital the next morning and wait for an opening in the doctor’s schedule. I stay with the children. She gets her tests, as well as some reassurance that the cancer hasn’t spread.

As Betsy goes off to her vacation, I get back on a plane. Looking out the window, it’s the same Atlantic that I’ve now seen so many times. But with each crossing, it gets a little smaller.