My sister is in prison. In October, she writes, I'll get to see the sky. She anticipates freedom, but thinking of it too much undoes her; she tries to stay in the moment, to cling to her daily routine of reading and yoga and sleep. Her one solid plan upon release: To eat a milkshake mixed with candy bars.

Last year, when she was in holding at the county jail they had video calls—a costly kind of prison Skype—and we synced her image with the television on Christmas morning. We stared at her in widescreen and she looked away, suddenly embarrassed. Rather than too many of us talking at once, the room was silent. We pointed our end of the camera at our Grandma, who didn't have a computer and so never got to see her, but this, she said later when she called on the landline, made her feel deeply ashamed.

To pass time, my sister spends long hours drawing coloring pages for her children: bunnies for Easter, turkeys for Thanksgiving. She makes them elaborate hidden pages, too—colored sea floors or forests complete with a finder's key. They discover a turtle camouflaged in tree leaves, dog bones in the trunk folds, a heart in the bushes. My children hunted for these treasures with their cousins once. My daughter wanted to write her aunt a letter back. They don't allow you to write in marker, her cousin warned. In case someone puts drugs in the ink. In my young niece's imaginings, inmates huff the bright markings on letters from home.

I write to her twice a week, printing out poetry and magazine articles. I wire money to her commissary account so she can buy phone cards or soda. She's been devouring books from the library cart: Moby Dick, Number the Stars, A Visit from the Goon Squad, Northanger Abbey. We have surprisingly similar tastes, something I was unaware of. I didn't know she liked to read. I don't think she knew, either. She used some of her money to buy a small radio off her former cellmate. "Have you read A People's History of the United States?" she writes. "I heard of it on NPR."

It's the closest we've been in our lives. I spent our childhood ditching her to play with the neighbors. I didn't want anything to do with her then and later, when we were more grown up, she got hooked on heroin and didn't want anything to do with me. What we have now is a circumstantial kind of closeness. When she gets out, I worry that I won't know how to stay close without the letters, without her desperation for my friendship.

"Your support has made a world of difference in my little prison world here and will be something to take with me to the world outside of it," she writes.

Unlike my sister, I allow myself to project wildly into the future, thinking of her coloring at the table with her children, of next Christmas together, her first yoga class, that milkshake.