Philadelphia confidence men Blue Howard and Johnny “White Folks” O’Brien are delighted when their latest “mark,” an older Italian-American man named Frascatti, falls for their “phony rocks” scheme, in which they convince him that Blue has stolen a fortune in diamond jewelry, which Frascatti buys for $10,000. Although Folks is African American, as is the older Blue, his father was white and his skin is so light that most people assume that he is white, making him trustworthy to the pair’s Caucasian targets, while Blue gains the trust of black marks. After Frascatti leaves, Blue and Folks meet at their apartment in a black neighborhood, where they congratulate each other on their profitable score. Cleo, Blue’s much younger wife, disparages Folks’s partnership with Blue and calls him “Trick Baby,” the derogatory name given to illegitimate children of black prostitutes and white “johns.” Disgusted, Blue explains that Folks’s mother, who was as dark as Cleo, was married to Folks’s white father and was not a prostitute. Meanwhile, Frascatti learns from fence Greenblatt that the diamonds he bought are glass, and the stunned man has a heart attack. At the hospital, Frascatti is watched over by his hot-headed, Mafia-connected nephew, Nino Parelli. Parelli is approached by corrupt, African-American police detective Dot Murray, who informs him that Frascatti was swindled by two con men. While Dot is assuring Parelli that he can apprehend the culprits, Folks notices Susan, a pampered woman who has come to his neighborhood to visit her dressmaker but is terrified of being alone on the street, surrounded by black people. Folks hails a cab and rides with her, convincing her that he is an out-of-town businessman who wants to celebrate a just-concluded deal, and at the Parkview Hotel, Susan admits her irrational fear of “all those black faces.” Folks, who has not revealed his real ethnicity, teasingly covers his face with burnt cork, but despite her initial irritation, Susan succumbs to his charm and the couple makes love. Later that evening, Folks joins Susan at a dinner party at which her condescending friends discuss how to prevent race riots by co-opting African Americans. Assuming that Folks, who goes by the name Johnny O’Brien when he is with Caucasian marks, is white, Dr. Howard Morrison and Paul Phillips are intrigued when he mentions that he is going to buy a block of tenement-houses, then resell the property to a shopping mall contractor for a large profit. When he asserts that he cannot include them in the deal, as he already has investors, Folks ensnares Morrison and Phillips, who beg him to show them the property. Folks calls Blue to inform him of the new scam, then tells Morrison and Phillips that in order to protect their privacy, they must bring $90,000 in cash the following morning when they view the site, while he will bring $10,000 to cover his share. Leaving the greedy men, Folks joins Blue at a nightclub where they are planning the upcoming deal when they are interrupted by Dot, who demands that they pay him $5,000 or he will reveal their identities to Parelli. The con men are horrified to learn of Frascatti’s Mafia connections and agree to the bribe, although they persuade Dot that, in order for them to have enough time to leave town without him double-crossing them, they will mail the money to his precinct house, along with a note incriminating him in the scheme. If Dot tells Parelli about them before they leave, they will warn the police commissioner about the note. Dot fails to see Blue substitute a wad of toilet paper for the money in the envelope before it is mailed, and later, as they drive along, a worried Folks demands that they leave Philadelphia immediately. Blue, who took Folks in when he was a boy and trained him in “the con,” assures him that they will have enough time to pull off the real estate scam before Dot receives the rigged envelope. The next morning, having found a vacant lot and office, Folks takes Morrison, Phillips and their friend, Dr. Carlson, to see Blue, who pretends to be a real estate agent. Although Blue acts nervous, asserting that Folks and he have other investors, he agrees to show them the property. They go to the vacant lot, where they tell the men that the adjoining block of tenement-houses is for sale. Back at Blue’s office, Morrison pressures him to accept their money instead of waiting until the following day for the other investors. Morrison sweetens the deal with an additional $30,000, although Blue and Folks are nonplussed when Morrison insists on keeping the money overnight in a safe-deposit box, as Blue has stated that he will not have the deeds until the next day. The con men recover by persuading Morrison to make them the signatories on the box, and soon the $130,000 is in the bank. The men part ways, with Blue waiting at the bank for Folks’s return, but before Folks can get back, he is stopped by Dot, who is suspicious that Folks is still in town. Folks is able to elude the policeman, but by the time he returns to the bank, it is closed. Folks wants to flee, as Dot will soon realize he has been tricked and alert Parelli, but Blue insists that they must wait until the bank opens, as there is too much money at stake to leave. Believing that their “flow” is gone, however, Folks declares that he is going to Chicago. Meanwhile, Dot has received the trick envelope and, after ransacking Folks’s and Blue’s apartment, spots Folks on the street. Dot shoots Folks in the upper arm, but the wily con man escapes after a long chase. Dot then goes to Frascatti’s funeral, where he tells Parelli the names of the two “colored” con men, and Parelli promises Dot a reward, but sends his own thugs after Dot because he does not trust him. While Blue searches for help among his friends, who, knowing that he is “hot,” refuse to aid him, Folks goes to a hotel room where Susan waits for him. She tends to his wound and when Folks confesses to her that he is black, she asserts that it makes no difference. Knowing that she could never fit into his world, however, Folks leaves, then goes to the flophouse where he and Blue conned Frascatti. There, Blue laments having brought Folks into a life of crime. Dot and the two thugs arrive soon after, although the con men elude them and, as they drive, come across street preacher Josephus, an old friend of Blue. Josephus agrees to hide them, but Blue, realizing that Folks needs a doctor, borrows Josephus’ truck and drives Folks to the nightclub to get their pal Doc. There, Blue finds Cleo, who, angry that Dot ransacked their apartment, yells out Blue’s name, thereby alerting Parelli’s hoods, who have entered the club. Seeing them, Blue exits and when the men stop him, claims to be Rev. Blue Montgomery, not Blue Howard. His subterfuge is uncovered, however, when a drunken Dot lurches forward, yelling that the reward for Blue is his. The criminals shoot Dot and Blue, but when Folks jumps from the truck and races toward them, they believe that he is a white witness and run away. As Folks cradles the mortally wounded Blue, the old man whispers superstitious instructions to him about how to identify potential marks, then dies.