"Because if the heartbeat becomes too slow or too weak, then the life of the patient may be forfeit!" The Doctor snapped, "There, you have your answer, now leave me be!" He didn't like this conversation, and he didn't like the other mans imposition upon his time. He had work to do, and he had to return to his patient, and he did not wish to spend his time humoring this ruffian on the matter!

Finally, the shopkeep turned back towards them, and the Doctor let out a silent sigh of relief, as he extracted the mans payment from his pocket, and handed it across the counter.