he listened to the man 's heart for a few seconds , and i thought it must be a trick of the light , for i spied what appeared to be a smile playing on the doctor 's lips . `` let 's take a walk , child , '' dee said . `` oh , honestly , if you do n't take care of yourself you 're going to keel over from a heart attack . not even several thousand miles distant from it . ' they usually worked late and when they did n't , they were exhausted . 