How does the author use foreshadowing in Jack and Jill?

In Part II of the novel, there is another murder in the Truth School case, proving that Chop It-Off Charlie was not the killer. When Cross rushes to investigate this murder, he once again runs into Christine Johnson, the beautiful principal of the school. As Cross speaks to her, the reader can sense his fascination with this woman, foreshadowing a time when Cross might reach out to her again.