Caves Boimler, Mariner, Tendi, and Rutherford are trapped in a collapsed cave while on an away mission to study aggressively growing moss. With communications blocked, they await rescue and recount tales of previous experiences trapped in caves: Boimler was trapped with conspiracy theorist Lieutenant Levy on Kyron 4, but bonds with him when his theory that the cave is test by the mysterious Vendorians proves correct. Rutherford recounts how he and Dr. T'ana were trapped on Balkus 9, and he gave birth to an alien baby, whom he and T'ana raise together while searching for a cave exit. Mariner was trapped after leading an away mission with Delta Shift on Glish. Though initially oppositional with each other, their teamwork allows them to signal for rescue. Afterward, worrying that their stories show their social groups may be changing, they begin arguing. The moss, revealing itself to be sentient, demands to hear Tendi's story: After partying following Tendi's first day, all four of them were trapped in a lift, but it resulted in them becoming friends. Tendi assures them that they will always be friends, even if their social circles grow. The moss is touched and they continue recounting stories to it. Secretly, the blocked communications are revealed to be a Vendorian test of their friendship.