Danny and Baez set out to find a serial killer who has swiftly killed two people, but they have difficulty finding a connection between the victims. When they discover that one of the victims, an elderly lady, was arrested for murder, they question Trevor Holt, the ADA on the case and a mentor of Erin's who expresses anger that she was never convicted. After the serial killer strikes again by killing an ex-convict, Erin learns that Holt has inoperable pancreatic cancer and suspects he could be committing the murders as part of his bucket list to get vigilante justice. Once records for Holt's early casework connect him to the first victim, Danny and Baez intercept Holt as he is about to carry out another murder, but he commits suicide before Danny can talk him down. Meanwhile, Frank helps an old friend come to terms with his alcoholism and make amends with his family. Jamie intervenes in a domestic dispute involving a case of mistaken paternity.
