In 1903,American seaman Henry Adams (Gregory Peck) is stranded penniless in England and gets caught up in an unusual wager between two wealthy,eccentric brothers,Oliver (Ronald Squire) and Roderick Montpelier (Wilfrid Hyde-White).They persuade the Bank of England to issue a one million pound banknote,which they present to Adams in an envelope (only telling him that it contains some money).The reason for this is that Oliver believes that the mere existence of the note will enable the possessor to obtain whatever he needs,while Roderick contends that it would actually have to be spent for it to be of any use.
Once Adams gets over the shock of discovering how much the note is worth,he tries to return it to the brothers,but is told that they have left for a month.He then finds a letter in the envelope,explaining the wager and promising him a job if he can avoid spending the note for the month.
At first,everything goes as Oliver had predicted.Adams is mistaken for an eccentric millionaire and has no trouble getting food,clothes and a hotel suite on credit,just by showing his note.The story of the note is reported in the newspapers.Adams is welcomed into exclusive social circles,meeting the American ambassador and English aristocracy.He becomes very friendly with Portia Lansdowne (Jane Griffiths),the niece of the Duchess of Cromarty.
Then,fellow American Lloyd Hastings (Hartley Power) asks him to back a business venture.Hastings tells Adams that he does not have to put up any money himself; the mere association will allow Hastings to raise the money he needs to start up a gold mine by selling shares.
Trouble arises when the Duke of Frognal (A.E.Matthews),who had been unceremoniously evicted from the suite Adams now occupies,hides the note as a joke.When Adams is unable to produce the note,panic breaks out amongst the shareholders and Adams' creditors.Fortunately,all is straightened out in the end,and Adams is able to return the note to the Montpelier brothers at the end of the month.