I love Alias Smith and Jones. I love both Messrs Duel and Murphy.
This episode adds Ms Jane Merrow, who I loved since I first saw her on Danger Man (in the states it was known as Secret Agent - the song; Secret Agent Man - was added as the state-side opening theme) love 'Jane Merrow' (qv).
This episode brings back terrific character actor, JD Cannon (as 'Harry Briscoe') of the 'Bannerman Detective agency ( the Pinkerton agency).
I can only hypothesise, but, it seemed, at this point, the 'powers that be' of the series were beginning to fall back on a steady, repeatable bunch of actors, and plots, in this case, being Harry Briscoe's (mis)adventures.
Be that as it may, the series was still riding on great actors, and good plots, and into this, they added Ms Merrow as (the questionable) 'sister Isabel'.
Ms Merrow's previous work on Danger Man (as well as The Saint) were not comedic roles, but, her role here, as the sister-on-the-run, enabled her to have a bit of humour, as well as pathos.
The 'boys' - Messrs. Duel and Murphy - are, as always, terrific (I heard that Mr Murphy always looked for the 'magic' he had with Mr Duel in this series, sadly, never finding it again).
I did not see this series when it initially aired I wasn't born yet 😉), so, it's 'weird', in a way, as I'm sure I'm not the only one, who watches, looking for .'something' in Mr Duel, which shows how sad, and depressed he was. I know - it's not how ANY show, should be watched. I can also guess that Mr Duel would not want anyone watching to be maudlin - he'd want to do one thing; entertain, and on this count, he - and the show - most certainly does.