When their parents go out of town on business they leave Frank, a studious, responsible college student, in charge of his high school aged sister, Johnna. Frank is to make sure Johnna did her homework, got to school on time - and stayed out of her usual trouble.
Johnna, as usual, has other plans. Her chief joy seems to be causing as much chaos as possible.
During a class trip to the closed community’s central laboratories, Johnna wanders off and discovers the unthinkable - her parent aren’t away on business, they’re floating in green fluid in two of several hundred identically occupied tubes in a lab deep underground. Before she can react and attract the attention of the other students, Johnna is silenced, arrested, and hustled off.
When Frank arrives to help Johnna he finds himself also under arrest. Now that they both know too much, the siblings can’t be returned to the community to talk. Frank and Johnna find themselves ‘volunteered’ for the same program their parents are in. Locked in the secret lab and strapped down to gurneys, the siblings have no choice but to wait and plan.
An interminable time later an orderly arrives to start IV’s, the first step in immersing the siblings in the green liquid. The siblings, by plan, play dead, waiting for their opportunity. The orderly, having trouble finding a vein to use, loosens the strap holding one of Johnna’s wrists. As the orderly turns back to his cart to get the IV, Johnna frantically, silently tries to wrench his wrist out of the loosened strap. Frank can only watch and egg Johnna on. As the orderly turns back…
Johnna frees her hand and grabs the orderly’s arm. The orderly, surprised, struggles, his hands full of equipment. He kicks out, sending the cart careening into Frank’s gurney. Frank searches the tray by touch, finds a scalpel and start sawing through his wrist restraint – and his wrist.
The orderly manages to wrestle himself out of Johnna’s grip and backs into Frank’s chair. With his wrist finally free, Frank grabs the orderly around the neck and cuts off his air. Unable to free himself, the orderly is forced to undo Frank’s restraints.
Once off the gurneys, the siblings talk the orderly onto their side. The orderly starts to help them, but betrays them, tazing Johnna. Frank stabs the orderly with the scalpel but gets pushed into a container. With his last ounce of strength, the orderly closes and locks the container and starts the process of filing it with the green liquid.
As the green liquid rises, filling the container, Frank watches Johnna being put back onto his gurney and strapped down even tighter than before. As the air is pressed out of the container, Frank first holds his breath and then becomes still, floating in the neutral density fluid.
When Johnna wakes, she can’t find Frank, as the gurney she’s strapped to is pointed the wrong way. Naturally, Frank doesn’t answer Johnna’s calls. A doctor and orderlies surround the container, with Frank’s body quietly floating in the green fluid. Gibson, the very old man who owns the community and the laboratories, is constantly checking on Frank’s status. Far from being dead, Frank is alive; the fluid is maintaining his body and his brain is showing a minimal amount of activity – something all the previous bodies lacked. Gibson wants Frank extracted from the fluid and restored to life.
Gibson eventually arrives and Frank’s tank is drained and his body removed to a gurney and strapped down. In spite of no longer being immersed in the fluid, though, Frank doesn’t wake and he shows no more brain function than he did in the tank. Gibson order’s Johnna removed from the gurney and handcuffed, via a long chain, to the far side of the lab. Over time Frank’s brain activity increases and everyone, including the guard assigned to watch Johnna, becomes fascinated by the process. In a moment of distraction the guard moves just close enough…
Johnna wraps the chain around the guard’s neck and snaps it tight. The guard silently tries to free himself from the chain and breath. Johnna wraps the chain around them both, trapping the guard’s arms to his chest, and pushes hard again the wall. The two struggle in silence and the others in the lab concentrate on Frank’s condition. The guard finally passes out. Johnna unwinds the chain and starts searching the guard’s pockets for the handcuff keys.
Frank finally does wake and Gibson takes them to see the real reason the green-fluid project was started, why the community is closed, and why he so desperately needs Frank’s knowledge based on a paper he wrote for his quantum-astrophysics class.
This little closed community is all that’s left in the world following an atomic war and the radiation is leaking into the outskirts of the fields that feed and surround the community. What’s left of the human race must leave the planet and the only way is by slow generation ships.
Except, as Frank assures Gibson, slow ships aren’t the answer. His theory proves faster-than-light ships are not only possible, but necessary. All those people were ducked in the green fluid for nothing.