Passing begins with Quincy (Jack Klugman) and Sam (Robert Ito) eating at a roadside diner while traveling back to LA from a pathologists convention. A motorcycle gang enters the diner and an uneasy Sam rushes Quincy out the door, but as they walk to the car Quincy notices a human skull on the handlebar of one of the motorcycles and begins to examine it. Following a brief confrontation with the biker, Quincy buys the skull from him and returns to the lab to investigate who the skull belonged to and whether or not they were murdered.
A forensic artist (Zohra Lampert) is called in to assist in the case by doing a facial reconstruction, and the investigation leads them to believe that the skull may have belonged to a missing union leader. The only problem with that theory is that the skull is further determined to be of an African-American male, but the union leader was white. Meanwhile, a rival union leader tries to intimidate Quincy and the department into stopping the investigation into the disappearance through scare tactics.
To me this was just an OK episode with a few problems. First off, when Monahan (Garry Walberg) presents Quincy with a huge list of names of men missing from the area over the past two years early in the episode, somehow Quincy magically pinpoints the correct person out of hundreds of names with absolutely no evidence yet to narrow it down. How was this possible?? I also found the facial reconstruction part of the plot to be a complete rehash of the story from Season 2's "...The Thigh Bone's Connected to the Knee Bone..." episode which had a very similar premise. Furthermore, I found the idea of a man being blackmailed and embezzling huge sums of money to cover up his racial ancestry which was not even apparent to anyone to be completely ridiculous. Even in 1978 which is when this episode aired, would this have mattered or changed anything in his already established life??
On the positive side, there is a murder mystery featured, but it is not compelling or interesting enough to overcome other flaws.