Two sentences from the story "The Chaser"

Here are two sentences from The Chaser by John Collier that I can't understand very well, and I hope you have read about this story so that i can just quote a few sentences to make the context.

"so," said Alan, "you really do sell love potions?"
"If I did not sell love potions," said the old man, reaching for another bottle, "I should not have mentioned the other matter to you. It is only when one is in a position to oblige that one can afford to be so confidential" 
 ....
"Oh, no," said the old man. "Their effects are permanent, and extend far beyond the mere casual impulse. But they include it. Oh, yes, they include it. Bountifully, insistently. Everlastingly."
"Dear me!" said Alan, attempting a look of scientific detachment. "How very interesting!" 

Thank you!