Jovial Willie O'Hara, a traveling, patent-medicine salesman, comes to Walnut Grove with his talking crow and chimpanzee "circus", appears to immediately cure Mr. Hanson's incurable headache and convinces most of the community that his remedy is good for anything, and everything, that ails them. But an angry Doc Baker must intervene when Mrs. Oleson believes that the potion will cure her life-threatening appendicitis and later, Laura learns a difficult lesson when she expects O'Hara's miraculous medicine to heal her seriously injured best friend...her beloved dog, Jack.
—shepherd1138