MISTER 880 is an elderly gentleman, Skipper Miller (Edmund Gwenn), who in his spare time has taken up counterfeiting to supplement his income. His brazen amateurishness, however, raises the ire of the treasury department. One treasury agent in particular, the hard-nosed Steve Buchanan (Burt Lancaster), decides to make it his mission to track down and prosecute the "mastermind" behind the counterfeiting.