John Kresge (played by John Pyper-Ferguson) was a detective in San Diego who worked on the murder investigation of Marshall Sim's wife. During the Christmas reunion, Dana Scully became involved after receiving unusual phone calls that sounded like her deceased sister Melissa. Scully found herself becoming more and more involved with the case, particularly in regard to Emily Sim. Kresge assisted Scully during the investigation despite his initial annoyance at Scully's constant presence near what Kresge deemed a local matter not suited for the FBI (TXF: "Christmas Carol").