It was a cool, breezy morning in Wichita, where I was visiting my sister for a few days. We decided to head to the zoo, figuring we could get some exercise while also viewing the array of birds and beasts.

While we walked around the zoo, I thought of the times in our childhood when Rosemary and I journeyed side by side. All the days we walked home from the school bus stop together. The times we played outside, galloping across the yard on our make-believe horses.

I also recalled the first time we saw a horror movie and how glad I was later that she slept in the bed across from me. As author Jandy Nelson put it, “There were once two sisters who were not afraid of the dark, because the dark was full of the other’s voice across the room.”

There are two famous sisters in the Bible, Mary and Martha, and their different personalities reveal how far apart sisters may be. One is a worrier, dashing around anxiously to serve Jesus, while the other sits prayerfully with him, heeding his words.

I tend to be the worrier, who examines every possible outcome before making a decision. The pluses, the minuses, the potential disasters, the probable joys. My sister is more prone to take a leap of faith and trust God will be there to steady her.

For a long time, when I was in college, we took very different roads, as my sister raised three children and devoted herself to home and hearth—while yours truly got involved with radical political causes. But whenever I visited, there she was at the airport, eagerly searching the faces in the crowd until she spotted me.

As we arrived at a zoo exhibit marked “tropical,” I pulled myself back to the present moment. There were clusters of fancy birds roaming freely through the lush greenery and a few darting across our path.

We sat down on a bench and did what most people do when sightseeing—took some selfies. I asked my sister how to edit photos on my phone and she showed me a few tricks.

Soon we headed back to the car, feeling we’d had sufficient exercise for the day. It was then that Rosemary realized her phone was missing.

“I bet you left it in the tropical bird place,” I said, remembering the photos we’d taken there.

We hurried back to the admissions booth to see if a phone had been turned in—but no luck. Flustered, we tried explaining where we thought it might be and asked for directions. The lady pointed to the left, and we headed off, now switching to speed walking.

Soon a wandering duck spotted us and tried protecting his territory by running after us, wielding his sharp beak. As we scurried away, we reminisced about the pet ducks we had as children—Dippy and Dopey—and how we’d led them around on leashes made of ribbons.

And I thought of a quote by Marion Garretty, “A sister is a little bit of childhood that can never be lost.”

The story had a happy ending. An honest man turned in the phone, and it was soon back in my sister’s hands. As we headed to lunch, we started laughing uncontrollably when we realized we’d walked in the wrong direction to get back to the tropical exhibit—which means we’d logged about six miles total that morning!

The zoo adventure added another coin to our big memory bank, which includes playing with our pet turtles, Flat-top and Wormy, and battling each other with our stuffed dogs, Poppa and Wooshie.

The treasured bank also harbors remembrances of Christmas and the frenzied rush to the sparkling boxes beneath the tree. All the board games that often led to hurt feelings. All the vacations when we drew a line down the middle of the motel bed.

How deeply I cherish my sister as a part of me that can never be lost. Hers is the face I will always search for in the crowd. And her voice will always reassure me in the dark.