The episode starts with the US space shuttle orbiting the earth. The shuttle TV camera starts to malfunction, and they can't get it to work or follow any orders, so it's shut off. Back on earth, two technicians are working on the shuttle after it has landed. One of them, Crew Chief Simmons (John Ashton, from the "Beverly Hills Cop" movies) unattaches the camera, about the size of a large shoebox, to take it to be repaired. He picks it up, a blue light flashes and suddenly he disappears. The box falls to the ground, and the other technician calls for an emergency alert. The box is put in an isolation chamber. As the scientists are discussing what could possibly have happened to the technician, there is a bright flash in the isolation chamber, and suddenly Simmons is back again, but the box is gone. He asks to be let out and gets quite angry about the situation, but the scientists don't know what to think. They review the tape of the box changing into the man, but are stumped. Simmons tells them his name, ID number and everything personal they ask, but they don't trust him. He tells them he has to get out, and when they ask why, Simmons is gone and a woman stands there. She begs them to let him out, and one of the people says that it's Simmons' wife, Kathy. The woman answers to that name; obviously when the creature assimilates an object, it also takes on it's memories. They realize they have a creature who can change its organic structure at will. When Kathy begs them to let her husband go, a scientist asks her where her husband is, since she's alone in the iso tank. The creature has been caught in a misstep in judgment, and acts just like a person in that situation. She gets flustered and looks around, trying to cover up her mistake.

The blue light flashes again, and Simmons is back. He starts breaking things inside the isolation tank, and they pipe in sleeping gas. The man slumps to the floor. One of the doctors thinks it's safe to go in, and when he does, the man gets up, takes his hand, and they both disappear in a flash of blue light. In their place sits a nuclear bomb. The people on the outside remember, too late, that the doctor who went in was a bomb expert for the US nuclear team in years past. Another scientist bravely goes in (played by Terry O'Quinn), and tries to reason with the bomb, telling the creature that it will probably go on living after the bomb explodes, but the people in the complex won't. The timer gets to zero, everyone is expecting the bomb to explode. Instead, the doctor appears again, and runs out of the tank, which Terry left conveniently open.

Terry runs after him and finds the creature on a launch platform. He begs the creature to let the doctor and Simmons go, but the creature says they aren't prisoners. They want to stay; it's not like prison. It's a thirst that makes them want to go, the creature tells him. A thirst for knowledge. The creature asks Terry to come with them, join them in the adventure, but Terry can't find the courage. The scientist asks why the creature came to earth. "Just curious", he says. Then the creature changes shape to a gaseous glowing cloud, and flies away into the night sky.

Imagine yourself a visitor to many worlds; drifting on the solar wind. A thousand voices singing in your memory. Now imagine you're this man, who can only guess at the wonders he might have known. Wonders that exist for him now as a riddle . . . from the Twilight Zone.