The "Sugarman" (real name Robert Phillips) is the identity of several drug dealers in Riverdale. Though the identity has changed names over time, the current one, Mr. Phillips, is a school teacher at Southside High School. He gives no clue to his students as to his true identity, which is not revealed to the audience either until the end of Episode 19.
Mr. Phillips is introduced as an English teacher at Southside High School, one who Jughead connects with owing to his own passion for writing. Phillips is supportive of Jughead's work, though when he discovers that Jughead has joined the Southside Serpents, he voices his disapproval, citing their drug dealing as an example of their many vices. Jughead though, insists that drug dealing is committed by the Ghoulies gang, and not the Southside Serpents.
Simultaneously, Betty Cooper (who has been getting blackmailed by the vigilante Black Hood), is told to find a drug dealer known as "The Sugarman" so that he can answer for his crimes. Once cajoled into helping, Betty begins asking around, and learns from Cheryl Blossom that "The Sugarman" was a sort of boogeyman that her parents would tell her of as a means of keeping her in line, but Cheryl always assumed in retrospect that the stories were just that. However, after looking through some old drawings of hers, she discovers one she did of herself, her brother, and "Sugarman" that makes her realize that the Sugarman is real. She confronts her mother about it, and though her mother initially denies it, she later admits that, yes, in fact the Sugarman was real, albeit as an alias used by numerous drug dealers over an extended period. Reconciling with her mother (with whom her relationship had long been strained), Cheryl gets her to name the current Sugarman's identity; Mr. Phillips. Cheryl then informs Betty, who informs the police, who arrest Mr. Phillips at Southside High.
Though Betty had refused to give Sugarman to Black Hood for him to murder, he is somehow able to get past the guards in the prison where Mr. Phillips is being kept, and shoots him dead.