Phineas and Jeff save General MacArthur's life during the attack on Pearl Harbor and help Buffalo Bill Cody make his pony express run. They must also deal with an Army intelligence officer who travels in time with them.
After finding no Cape Kennedy in 1969 or no United States as well, Phineas and Jeffery return to the end of World War II to make sure that German rocket scientist Werner Van Braun doesn't far into Soviet hands.
In 1890 Jeffery can't call for a doctor when Dwight David Eisenhower's mother goes into labor because it doesn't exist. They travel to 1875 to make sure that Bell has is financing to continue his telephone experiments.