Nature was mean to allow human males to find fulfillment in bed after only a few minutes of frantic activity - after only a few seconds of it for lesser animals like rats and mice who then hurry off on their perpetual search for food - where-as women, as is well known but far too rarely practiced, need a slow build up and prolonged love-play to get to be properly 'ready.'
Our 'hero', the amateur therapist Harry Harrison, due to an unfortunate set-back that happened to his wife, gets to become well known and in demand in his immediate area due to his prowess at redressing nature's fundamental error.