Johan Tiger is an actor in Stockholm during World War II. A British agent in Sweden discovers that Johan is a dead ringer for General Lucky and manages to lure him over to London with a role as Othello as bait.

The marriage of the newlyweds Gun and Emil is strained when Gun sings in a radio show and makes a breakthrough.

In 1803 the Swedish inventor John Ericsson is born. After a military career he went to England and became one of the first builders of locomotives. Despite large debts, he invents the propeller. In 1839 he crosses the Atlantic and builds ships for the US Navy. When the US civil war breaks out, the Federation needs a ship to match the Confederate 'Merrimac' and preventing the Confederation from exporting cotton to Europe. Ericsson builds the 'Monitor', a ship the Federation needs to win the war.

The rejected artist Tore Nilsson disrupts the radio managers broadcast and gets his singing audition live on air.