Y/ N and Eli are selected for a government exchange program with the Verath, a deep ocean species with no empathy, where two humans go below forever in exchange for two Verath getting to live on land. They spend a month at an underwater facility with their assigned Verath pairs, Calla and Ori, undergoing physical and mental transformations that rewrite their bodies and minds completely. Calla spends the entire process eagerly asking Y/N about the surface life she is taking without once considering what Y/N is losing, because the concept of someone else’s pain simply does not exist in her yet. When the mental transformation completes Calla and Ori become fully human, gain empathy for the first time, and immediately realize they can never go back — the biological window for reversal has permanently closed. When a reversal is quietly offered to Y/ and Eli, Eli refuses instantly, but Y/N still has a choice, and Calla — now drowning in guilt she has no idea how to carry — is standing right there when she makes it.​​​​​​​​​​​​​​​​