Promise Not to Tell is a 2007 mystery novel with supernatural elements written by Vermont author Jennifer McMahon.

It was released in Germany by Rowohlt Verlag, under the title Das Mädchen Im Wald (The Girl in the Woods), in October 2007.

In 2002, Kate Cypher, a 41-year-old school nurse, returns home to her Vermont hippie commune where she grew up to care for her aging mother, who is afflicted with Alzheimer's disease.

Kate is drawn into the investigation of the modern-day crime, and must revisit Del's original murder, and her culpability in it.

By following these clues, Kate re-meets many members of the hippie town she grew up in and relives some of the horrifying times during Del's murder.