S01E14 (26th February 1970). Written by Robert Barr, directed by Ben Rea

In the course of another enquiry, WDC Donald learns that Chris Conner (Sean Caffrey) and his associates are planning a serious crime. But can Donald’s informant – Conner’s girlfriend Molly Carson (Imogen Hassall) – be trusted?

It’s always a slightly melancholy experience watching a performance by Imogen Hassall. Whilst it’s true that most of the actors in series of this age will no longer be with us, Hassall’s tragically early death (she took her own life in 1980 at the age of just 38) hits just that little bit harder.

Her film and television credits began to dry up in the early seventies, but at least her role as Molly is a substantial one. And apart from an Irish accent which comes and goes a little, it’s a fine one and held my attention throughout.

Donald, searching for a missing Swedish au pair girl, strikes up a friendship with Molly. John Watt (who despises female informers in general and Molly in particular) seems initially reluctant to accept her word on anything (at one point referring to her as a “bitch”). It’s just as well that he eventually comes round though, as everything she passes onto Donald proves to be true.

As for Donald herself, she literally has to be pushed into Hawkins’ office to share this lead. That she seems so hesitant could be partly due to her inexperience or partly because of her sex (Watt’s unbelieving comment of “and she came to you?” can be taken either way).

Sean Caffrey has the less flashy role of Chris Conner. Although we’ve been told that Conner is a violent criminal, at first (and especially round Molly) there’s little evidence of this. But Caffrey’s performance is a subtle one and prior to his arrest (where he puts up plenty of resistance – courtesy of a Peter Diamond arranged fight sequence) he manages to tease out the darkness that lies underneath Conner’s affable exterior.

Stephen Rea (as Conner’s brother Philip) has a handful of scenes whilst the other main guest performers are a gaggle of young British actresses who attempt to convince (well, they don’t convince that much) as foreign au pair girls. Their sing-song accents are a little too close to parody for my tastes.

It’s easy to tell this is a Robert Barr script (Conner explains how they’ll tackle the safe robbery in extreme detail – complete with maps and little model cars) but at least it’s one of his better ones. If there’s no particular twist in the tale – apart from the fact that Molly may not have been quite the victim she claimed to be – then it’s still competent enough.