February 2, 1866 his mother Elise writes Sister-In-Law: “This time the news I have for you is very sad. It has pleased the Lord to take from us the dearest thing we possessed on this earth, our most beloved child Thorvald. Of course, I love all my children beyond words; but Thorvald was so much younger than the others, and he was such a sweet, lovely child that he was his father’s and his mother’s favorite. Both he and Niels fell ill in the month of July; I believe that from that time the disease which finally caused his death was in his body, although he apparently had recovered. A week ago last Sunday, on January 21, we walked over to one of our neighbors after dinner, and Thorvald ran beside me, happy and gay as usual. After we had stayed a couple of hours with our friends, I had to go home to bring in the sheep, and I asked if any of the others felt like walking home with me; but they said they wanted to stay on a little longer. Only my sweet little Thorvald wanted to go with Mama. On the way home he chatted with me as was his wont, and there was not the slightest indication that anything was wrong with him. We had taken hardly more than ten steps, however, after his last words, when suddenly, without uttering a sound, he collapsed beside me. When I looked at him I could see that he had the cramps. I picked him up in my arms and carried him home as fast as I could and sent for Wilhelm and the doctor. Thorvald was ill three days and I am afraid he suffered a great deal. On the third day he spoke a little, but it was very difficult for him to pronounce the words distinctly. I was so unspeakably happy when he began to talk on Wednesday morning, for I began then to hope that God might still let me keep my dear child. But no, it was not to be; about noon he began to breathe more heavily, and around four o’clock he died. He was buried on Friday of that week.
I know that my little Thorvald now is happy with God – surely much happier than we could ever have made him here on earth – but I miss him so terribly!”

In June 1866 in a letter to Thomine Elise says “I must, however, tell you of a strange question that my little ‘Tulli’ asked me the night before he took sick, just as though he had a premonition of his impending death. He asked me if I didn’t think it would be too bad if he died now. Because I didn’t think there was the slightest danger that such a thing could happen, I was merely surprised and asked why. “Oh”, he said, “if I died would I always keep this bad breath which I have just now,” His idea was that the new body we get after death would be exactly like the one we leave when we die. I told him that our new body in all probability will have a certain likeness to our earthly one, but that it will be free of all defects and imperfections. He then asked me many things about resurrection and the next life, much more than I was able to explain to him. Now my little angel knows all that he wished to know – and all that is still a mystery to us.” Source "The Lady with Pen"