To catch a group of counterfeiters who murdered an investigator, Jennifer and Jonathan go on a cruise, she posing as a European countess and he working as a ship's steward.
Due to an airline strike the Harts have to travel from Chicago to Los Angeles by train. They unwittingly get caught up in a murder plot involving other passengers.
When Jennifer overhears an acquaintance and his mistress planning to murder his wife on the ski slopes, she and Jonathan jet off to Vail to prevent it -- but are they too late to save her on the ski trail?
Max has been taken hostage in order to train two Hart look-alikes to fool some wealthy people at a dinner. In a case of mistaken identity, the real Jonathan and Jennifer turn up, unaware of what is planned for them.
After witnessing a murder, Jonathan hits his head and loses his memory. As he tries to recover his memory, he starts to suspect he may have had a mistress -- and killed her.