Isaac didn't go to the pharmacy right away.  He went to his billet and made a radiophone call.

"Biological lab.  Struckheimer here."

"Waldo, this is Isaac Crowell.  Could I ask a favor?"

"Fire away."

"I'm going down to Dr. Norman's office now, to get some Gravitol.  Those tablets you gave me today seemed just about right - could you look up the dosage?"

"Don't have to look it up, it's five milligrams. But look, Isaac, he'll probably want you on a smaller dose - the older you get, the less they give you."

"Really?  Well, I'll try to talk him out of it.  Seems to me it should go the other way around!"

"You'll never talk Willy out of anything.  He's the most stubborn creature I've ever argued with."

"I know; we were good friends.  Maybe he'll have pity on a fellow geriatrics-ward case."
"Well, good luck.  See you again soon?"

"I'll be down your way tomorrow, checking out the wines."

"Stop in for a beer."

"Glad to."  They rang off.

Crowell emptied his suitcase and hipped up the false bottom.  He selected a stylus that was an ordinary ball-feed pen on one side and an ultrasonic ink eradicator on the other.  Luckily, the doctor had used a black ball-feed to write the prescription; he wouldn't have to forge the signature.

He practiced writing "5 mg. Gravitol, quant suff 30 days" a couple of dozen times, then buzzed the Pandroxin prescription into invisibility and scrawled the counterfeit one over the signature.

The Company store was dark except for one light over the prescription desk.  The front door was locked and Crowell dragged himself over to a side door.  It slid open when he put his foot on the treadle-mat, and a bell rang.

A clerk came from behind the shelves of reagents, rubbing sleep from his eyes.  "Something I can do for you?"

"Yes, I'd like this filled, please."

"Sure thing."  The young man took it and walked back behind the shelves.  "Say," he yelled back, "this isn't for you, is it?"

All Otto now.  "Of course not.  I use Pandroxin.  That's for Dr. Struckheimer."