Brennan's former professor and ex-boyfriend Dr. Michael Stires makes a surprise visit to the Jeffersonian while he is in town interviewing for a job. While Brennan and Dr. Stires are at dinner together, Booth makes a gruesome discovery -- the remains of a young woman decomposing in a refrigerator. As Booth and Brennan investigate the case, Brennan is called as an expert witness at the trial, but is shocked when the defense brings in a very familiar expert of their own.