"His blood. It is not blood that we know, that carries food and oxygen, and the toxics. It is alien. The cell structure is apparently designed to transmit—this is going to sound silly, and I haven't the opportunity of checking my first impressions, to make sure—but the cells appear constructed to transmit pure energy in the form of sheer heat."
"But the tissues, girl! In a normal man the food becomes energy in the tissues. How—?"
"I don't know. Look for yourself."
She stood away from the microscope, gesturing toward it. Space Commander Mason bent to the screen. His right hand raised the electronic power a hundred units. He stood like that for many minutes, frowning, scarcely breathing. When he straightened, he looked at Tyr for a long time, breathing harshly.
He said, "It seems to be a blood that carries nothing but radiating heat pulses. That means he intakes his energy pure. The efficiency rate is perfect. Katha, he isn't a man. Not a man such as we know men."
Katha took Tyr by the arm and led him behind a fluoroscope machine, saying, "Stand here, please." Mason was eyeing him steadily as he walked in front of the screen.
Tyr grinned to himself. They were in for a shock, if this machine did what he thought it did.
The room darkened. A pale green glow came and pulsed. The plate before him seemed to hum softly. The dark blobs of shadow that were the Commander and Katha moved suddenly and grew still. Deadly still.
"The machine is wrong!" croaked Commander Mason.