When Americans are detained in North Korea, they can expect harsh conditions, with tiny prison cells, little food or water and even less daylight. And their story line is preordained: A forced confession, a show trial, a sentence to years of hard labor with little chance of appeal.

The release of Otto F. Warmbier on Tuesday leaves three American citizens known to now be held in North Korea. Two were arrested in the last two months; Tony Kim, also known as Kim Sang-duk, on April 23, and Kim Hak-song, also known as Jin Xue Song, on May 6; the North Korean authorities accused each man of “hostile acts.” Little is known about the case of the third American, Kim Dong-chul, including why he was detained in 2015.

The experiences of other Americans who have been detained and eventually released by North Korea, often with the help of prominent American politicians, crack open the door on the secretive regime’s network of prison camps and the deprivation found there.

“It was a 5-by-6-foot cell, and there were a couple of slats on the doors,” Laura Ling, a journalist detained in 2009, revealed in a magazine interview after her release. “There were no bars, so you couldn’t see out, and if they closed those slats, it just went completely dark. There was no way to communicate with the outside world.”