Jack Costello is a retired cop and now private detective who lives in Miami, who handles a myriad of cases for unusual clients. At his side are old police buddy Sam Bosley and cartoonist-turned-amateur sleuth Jean Philippe Dumas, who is using Costello as an influence and has nicknamed the burly detective "Extralarge." In the second series, Costello faces other dangerous cases, again with Bosley and Archibald, the son of an old friend, who Costello amusingly nicknames "Dumas."