In Lexi and Lister Defeat Death, Lexi lives with Agnes and 'Dr. Joe' Lister, the Father of Modern Surgery. Dr. Joe's concern about deadly infections following surgery, and his work with scientists Thomas Anderson and Louis Pasteur, lead him to develop antiseptic methods to prevent infection. His first case is their mischievous kitten Bart 'the Brat' and his second is 11 year old Jimmy Greensley. As word of Dr. Joe's success spreads, he becomes the victim of ridicule. But Dr. Joe's perseverance and confidence in his new life-saving techniques win over the medical community.