When Jonas Salk sees his neighbors incapacitated by the polio virus, he knows it's his chance to apply the Jewish concept tikkun olam-healing the world. By reading books, learning math, and training to become a scientist, Salk invents the vaccine that would cure polio across the globe. Dean Robbins's captivating prose and Mike Dutton's colorful illustrations demonstrate how one person's bravery and altruism can help heal the world. With an informational author's note and a timeline of the invention and implementation of vaccines, this picture book with STEM connections will appeal to history buffs, science lovers, librarians, and teachers alike.