On the surface, the story follows a mute woman, Elisa (Sally Hawkins) in the 1960's, who works as a janitor at a government laboratory. The laboratory's immediate concern is the space race and their newest "asset" (a human-adjacent fish creature played by Doug Jones) could provide insight into how men would survive in previously unknown conditions. It's quickly apparent that this is no creature, but a being capable of emotion, intelligence, and thought. Unsurprisingly, his handler Strickland (Michael Shannon) is incapable of seeing anything other than an assignment that must be contained & controlled by any means necessary. To the military, this thing is simply a means to an end, but Elisa quickly sees (and brings out) more.