Monkey wrench blues: A race that could spell life or death for the girl detective! Hinkley is able to build a prototype for a new high-efficiency car based on a recently recovered engine. After seeing Nancy drive a tank and stop a speeding train, he wants her (and mechanic Bess) to drive the prototype in a government-sponsored race. The car with the best fuel efficiency wins a government development contract, money Hinkley and Credo would need to bring the car to production. But someone is determined that Nancy and Bess lose, at any cost!

Dress reversal: When Bess and George help Nancy pick out a dress for Deirdre's big party, little do they suspect it's the identical dress Deirdre will be wearing. After a minor altercation with the perturbed hostess, Nancy leaves the party only to be grabbed by a dark figure, tossed into a van and kidnapped! That leaves Bess and George, with some help from Ned, to try and solve the mystery of exactly what just happened to Nancy. Things get complicated further when Bess and George's number one suspect, Deirdre, is kidnapped too!