Final appearance of original character Sgt. Bill Wells, who stayed the longest of the original three station sergeants. An integral part of the novels on which the series is based, actor Paul Moriarty's availability was affected by his ongoing role as George Palmer in EastEnders (1985), however once he left that show he was not brought back to "Frost" as Sgt. Wells, despite the series continuing for another 10 years. The involvement of the station sergeants was subsequently heavily reduced to Sgt. Brady, who was introduced the previous season and remained with the show for the rest of its run.
Based on the two other major plot lines in the fourth (and then-recently published) Frost novel "Hard Frost".
The first episode in which someone other than David Jason is credited above Bruce Alexander as Supt. Mullett, being Susannah Doyle as D.S. Liz Maud.