Anne is at Weatheroak Hall Maximum Security Medical Research Unit.  She’s there to meet Doctor McEwan (Barry Jackson) and Professor Alec Hetherington (Morris Perry) who have developed a revolutionary process to deal with hardened and psychopathic criminals.

Behind a glass panel she observes Michael Beavis (Michael Hawkins) receiving treatment.  Anne is horrified to learn that he’s essentially little more than a radio-controlled puppet – electrical impulses, controlled via a computer, damp down any negative or violent feelings he may have and McEwan is convinced this will enable him to be reintegrated into society (otherwise Beavis would remain a prisoner in Broadmoor and therefore a severe drain on the nation’s finances).

But for Anne, Beavis isn’t cured – his psychopathic tendencies are simply being suppressed.  Apart from the ethical issues this raises for her, she’s also far from convinced that the treatment is foolproof.  McEwan is happy for her to speak to Beavis on a one-to-one basis in order that her fears may be allayed, but by doing so she re-opens his long-buried trauma and after attacking her, he escapes ….

Hair Trigger was tapping into something of a zeitgeist about how technology could deal with violent criminals.  This was a theme of A Clockwork Orange (both the original book and the later film) whilst the 1971 Doctor Who story The Mind of Evil  also had its own method of removing evil impulses from the minds of criminals (an alien parasite).  Although the Doctor Who story was much more fantastical than Hair Trigger,  there are some similarities – not least Anne’s statement that by suppressing all the violent tendencies from any given subject they’ve basically been neutered and aren’t really human beings any more.

Director Quentin Lawrence creates a decent visual joke as the episode title and writer credit is displayed following the opening credits. They’ve overlaid over what appears to be a pastoral scene, but a few seconds later it’s revealed to be an album cover of classical music, which Anne puts onto the turntable as she attempts to convince Quist that McEwan’s process is fundamentally immoral.

Quist is slow to agree (although there’s the suggestion later that he was playing devil’s advocate). That Anne is the one who’s concerned whilst Quist remains a passive onlooker is another example of the way his role was downplayed during series three. He acts as a decent sounding board for Anne to develop her arguments, but apart from that Quist has little involvement in the main narrative.

The rest of the Doomwatch team are also pretty much surplus to requirements in this one. Bradley is absent, whilst Stafford and Barbara only have a couple of scenes. Although even in the limited screen time they both have, Barbara’s obvious dislike of Stafford is made quite clear.

Morris Perry and Barry Jackson both give characteristically solid performances, but the acting honours must go to Michael Hawkins as Beavis. When we first meet him, Beavis is desperately keen and eager to please, although when McEwan gently tells him that Anne will want to talk about his past life there’s a strong sense that his former crimes (he murdered his wife and children) still trouble him.

This is therefore something of a story weakness. We’re told that McEwan’s work has a zero failure rate – yet as soon as Anne starts to probe Beavis about his history he goes berserk. And the computer control isn’t able to stabilise him afterwards, as he escapes from the compound and takes a family hostage.

If the Doomwatch team aren’t terribly well used here (remember that Anne isn’t actually a member of Doomwatch) then Brian Hayle’s script is still a tautly written and well-acted affair. As I’ve said, acting kudos must go to Hawkins, especially in the final ten minutes as the hostage situation plays out to an inevitable but nonetheless powerful conclusion.