Isaac Grossman is the main antagonist in the story The Origin of Laughing Jack. In the Creepypasta, Isaac lives in London, on the very edge of town, in an unidentified era (probably early Victorian times) and he had horrible parents, his father was a misogynistic alcoholic rapist and his mother hated Isaac with a passion. Isaac was suffering from lack of friendship and human contact, when suddenly, the narrative says a guardian angel took pity on Isaac

And sent him a gift for Christmas.

Isaac had never had any gifts before; and he delighted when he saw the box at the end of his bed. It read "A Laughing Jack in a Box." Isaac had never heard of Laughing Jacks, but he knew about jack in the boxes. Isaac was delighted nonetheless and opened the box. He listened to some music and then thought it broken when nothing happened, but suddenly an animated, living jack in a box sprang out and introduced himself as "Laughing Jack." Isaac was a child, so he believed in supernatural creatures without question. He accepted Jack as a friend because nobody liked him and his own mother had said "Who would want to be friends with a useless worm such as you?" Jack said he already knew all about Isaac, and he was proud to be his friend.

Isaac said he needed schooling; so Jack said he would be right there when he came back. Isaac did come back and they had a wonderful night telling stories and playing and Jack felt good for the first time.

However, one day, Jack and Isaac were pretending to be pirates, and Isaac sighted an "enemy" - the neighbour's cat, and so he pretended to shoot at it but he squeezed the cat, first in playfulness, then he went too far and squeezed the cat to death. Isaac was disturbed at his first killing but he threw the cat's corpse into the back yard and then was raged at by his mother, who said he had killed the cat. Isaac said his doll friend Jack had killed the cat but his mother didn't believe him. So, Isaac had to move to a different location for awhile.

Isaac moved away for about ten years, and when one day his father finally killed his wife in a drunken rage and was hanged, Isaac inherited the house so he returned home and continued working. Jack was looking so much forward to seeing his old friend because he had been stuck in the box for ten years, but it was a disappointing reunion. Isaac no longer believed in the supernatural and was much more serious now. Isaac then one day bought a woman home from a pub and Laughing Jack was stuck in his box, forced to watch them both chat and then begin to kiss. Laughing Jack had never seen kissing before, so he was intrigued, but when Isaac began groping the woman, she pushed away, so Isaac began beating her, and then finally killed her by bashing her head in with a candle. Isaac then disposed of the woman's remains, and lured another victim to his house, who was a young boy who had apparently laughed at Isaac. After he had tortured the young boy gruesomely and killed him in a macabre fashion, Isaac fashioned the victims' remains into a chair, and other furniture.

Isaac then bought home an old blind woman, who realized the chair was made of human flesh, and she fell down the stairs in her hurry to escape. Isaac dealt with her remains too, and Isaac then bought home a young girl who he force fed glass to and ripped her open.

Over the months, the shelf Laughing Jack stood on broke, and his box tumbled down, and the clown burst out, and greeted Isaac, chiding him for ignoring him for so long, but said they could play good. So Laughing Jack sliced off Isaac's tongue, and then stabbed his eyes and throat, and put him on his torture bench where he began killing Isaac. He eviscerated Isaac and chided him all the while for ignoring him. However, when Isaac died, it's said he looked happy.