Fern gathers Rose, Zinnia, and Holly in Rose’s attic to reveal the paperback Miss Parcae slipped her, How to Be a Groovy Witch. Fern argues the book is about taking power and proposes a spell—Turnabout—to transfer Zinnia’s constant vomiting to someone else, despite Zinnia’s skepticism and Rose’s mocking.

Over the next three days, the girls quietly prepare by getting on kitchen duty and stealing or scavenging ingredients: peppercorns, an egg, lemon juice and peel, and pine needles; Holly sews a sachet. In the attic, Zinnia strips to her underwear and lies on the floor while Fern pricks her finger and rubs blood onto the egg. The three girls chant “Rise and fill” while sliding the egg over Zinnia’s belly until the egg unnaturally darkens—first black-gray, then a bruised purple—convincing them something real may be happening.

To aim the spell, they add three hairs stolen from Dr. Vincent’s office chair to the sachet and tie it shut. The next day, Fern and Holly volunteer to clean the Barn; while Holly watches for Nurse Kent, Fern hides the witch bag behind a drawer in Dr. Vincent’s desk.

That night they synchronize watches and plan a timed test during Fern’s clinic appointment so Zinnia can match smells (lemon juice, then Pine-Sol, then Lysol) to whatever happens to Dr. Vincent. Fern tries to stall in the clinic, then provokes Dr. Vincent into a long lecture about her blood pressure and the dangers to the baby, buying time until the planned moment.

At exactly the target time, Dr. Vincent suddenly turns gray and begins violently vomiting, first into his handkerchief, then the wastebasket, repeatedly and uncontrollably. Fern calls Nurse Kent in with feigned concern; as the retching escalates, Dr. Vincent “fire-hoses” vomit across his desk and then sprays Nurse Kent, soaking her uniform and even filling her shoes—an apparent confirmation that the Turnabout spell has shifted Zinnia’s sickness onto him.