“I concealed our serum,” Rod went on slowly, “from the tetrarchs by burying it in my arm. I had to get a hypo needle before I could use it here.”

“Have I had a fever, Rod?” Mona’s grey eyes were open. “Or is this delirium?”

Rod Harrow crossed to her swiftly. He cradled her head in his arms. She was smiling again—relaxed.

Then he turned to Williamson. “Line ’em up, Bill. With five liters we can inoculate every human on Tetrarch IV. There’ll never be a gryxon glow again.

“And as soon as a company has had all men injected, send them to the cave to bring back the reserves. We’ll need their help.”

“To celebrate?” Williamson wanted to know.

“Not particularly.” Rod was impatient. “We’ll have to do some planet cleaning.”

“Planet cleaning!”

“Right! We’re ready now to wipe the tetrarchs off our Earth.”