Charles Santore was in the middle of illustrating the children’s book he did not know would be his last when he began to feel weak.

The book was “The Scroobious Pip,” Edward Lear’s nonsense poem about an uncategorizable creature: part beast, part bird, part fish, part insect. The man bringing it to visual life was a beloved illustrator, a master of realism whose versions of “The Night Before Christmas,” “Peter Rabbit” and “The Wizard of Oz” have sold hundreds of thousands of copies.

Over the course of his career, Charlie, as he was known, rarely missed a day in his studio, two blocks from Rittenhouse Square in Philadelphia. But suddenly, he found himself in so much pain that he was unable to work.

On Aug. 11, 2019 — only six days after he was admitted to Pennsylvania Hospital — Charlie died. He was 84.

Soon after, his friend and agent Buz Teacher called a meeting with Charlie’s three adult children to discuss their father’s work. Among the most pressing questions was how to proceed with “The Scroobious Pip,” which was under contract with Running Press, a Philadelphia-based imprint of Hachette. Charlie had made nine drawings for it — each one an incredibly detailed menagerie — and three watercolor paintings. But there was an enormous amount of work left.