What is the climax of the Face on the Milk Carton?

The climax in the book takes place in chapter 17.  Janie places a summary of the details of her kidnapping in one of the envelopes she had typed her return address onto in typing class.  Later, "feeling spooky," she addresses the envelope to the Spring family.  On her way to her last class, Janie looks for the envelope and finds it is gone.  In a panic, she rushes to find Reeve so she can get his sister Lizzie's phone number.  At the end of the chapter we find out that she intends to have Lizzie call the Spring family before they receive her letter in the mail and call the police.