Serpico looks for the killer who targets women campaigning for mayoral candidate Gene Rincon. After Serpico discovers that a shady real estate businessman has contributed money to Rincon's campaign, he suspects that Rincon himself is involved with the murders.

Serpico is assigned to protect a witness who is scheduled to testify before a grand jury in three days. Sullivan assigns Carol Hinterman to assist Serpico, who has his doubts about her abilities. Mobster Vitorio La Bella is desperate is kill the witness at any cost.