Longfellow Deeds est un homme simple et naïf vivant dans une petite ville américaine. Sa vie est bouleversée quand il apprend qu'il vient d'hériter de 20 millions de dollars. Il se rend alors à New York pour toucher cet héritage. Là, il est la cible d'avocats véreux et de journalistes peu scrupuleux.
Joel and Garda Sloan, a husband and wife detective team, who also sell rare books in New York, take a vacation to Seaside City. At Seaside, Joel's pal, Mike Stevens is managing and preparing for their beauty pageant. Joel is made one of the judges plus he has invested $5,000 in it, to Garda's dismay. Eric Bartell, promoter, arrives to dupe Stevens. When Ed Connors, New York racketeer arrives, Bartell is mysteriously murdered. Joel and Garda set out to investigate the murder.