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In the Calder Bridge exchange program, human volunteers transfer their consciousness into alien Clessari hosts in the name of understanding and cooperation. Marrow enters the program believing in its promise—only to encounter a system that treats identity as a resource and loss as an acceptable metric. As she adapts to life inside a body shaped by psychic resonance and collective awareness, Marrow begins to witness the quiet failures buried beneath institutional language: hosts who never fully return, memories that fracture instead of healing, lives reduced to “acceptable variance.” The Clessari are expected to endure these costs without protest, while human administrators refine the program to survive scrutiny rather than confront its harm. Caught between bureaucratic indifference and alien resistance, Marrow must decide what it means to act when exposure does not guarantee change. Her intervention does not dismantle the system—but it alters who must carry its weight. What Remains Unreturned is a quiet, unsettling science fiction story about cultural extraction, ethical compromise, and the limits of testimony. It asks what responsibility remains when truth is acknowledged, archived, and allowed to continue anyway. Comparable works include The Left Hand of Darkness, Arrival, Never Let Me Go