“DNA Designs,” John announced as the door opened.

“I want my money back!”

The customer was a frazzled woman in a tan coat. The boy at her side wore a miniature navy suit with cuff links. His nose was running.

“Did you buy a warranty?” asked John.

“Your best.”

The woman held out an electronic notepad. John hooked it to the system.

“One healthy achiever Build-a-Son…” he read. “Immunity genes spliced in and switched on… EQ activated through mild OCD … Looks good to me.”

“But it’s all gone wrong!”

“Where’s your proof?”

“Look at him. He’s always got a cold. I’ve got a note from his doctor…”

John leaned forward. “You ever heard of the hygiene hypothesis?”

“Hyge—what’s that?”

“It’s a germ theory, says when parents keep the house too clean, kids get sick. How do you know that’s not the problem, instead of his genes?”

“That’s ludicrous–”

“Can’t prove it, can you?” John returned the electronic notepad. “You’ve got to rule out environmental factors. No proof, no refund.”