Just Desserts, Knot My Problem

Phineas and Ferb build a wall for climbing. Candace is recording a Fireside Girls book with Irving and loses her voice. Meanwhile, Dr. Doofenshmirtz creates the Just-Desserts-inator.
Candace thinks she can trap the boys at last when they ask her to call Mom if they get stuck in their giant Gordian Knot, but is distracted by helping Jeremy open his mini-safe.