Dead Stop begins late at night with two truckers dumping hazardous chemical waste in an unauthorized location. When one of them becomes exposed to the fumes, he quickly falls ill and dies the next day. Quincy (Jack Klugman) conducts the autopsy and is perplexed by the findings which indicate that the victim died from coming into contact with a contaminant rather than a heart attack, and this leads to an investigation into the source. When Quincy learns that the death was likely caused by inappropriate disposal of chemical waste, it becomes a race against time to locate the dumping site before others are poisoned and killed.
While there isn't a mystery featured in this episode as we see the cause of death right in the beginning and it is arguably more of a case of gross negligence rather than an intentional crime, I found it to be a reasonably decent episode. The story is not the most original as we've seen these race against time to avert a public health crisis episodes many times before with one of them even featuring an illegal offshore dumping plot, so it does lose a point from me for that. On the positive side, there are several highway scenes shot on location which I found to be interesting and different from the norm.
Overall this is a competent and fairly entertaining Season 7 episode which is not exactly what I would characterize as a must-see, but still a worthwhile entry for fans of the series.