Mabel Havelock and Violet Ficher are on a scenic bus tour of the Nordic capital cities of Europe. While touring the historical sites, they encounter a case of mistaken identity. Adding to the mystery are smugglers and thieves.

Then, when they reach Moscow, the tour becomes deadly. There is a busload of suspects to choose from. A flirtatious woman and her jealous husband. A professor of Nordic History who is ill-informed. Two world travellers who describe themselves as gypsies. And a mysterious man. The tour director's assistant and bus driver also have motives.

Unfortunately, the prime suspect is Mabel. She and Violet will have to use all their skills and ingenuity to solve the murder in Moscow and prove to the Russian police Mabel's innocence.