THE final act twist is one of the oldest tricks in the dramatist's book. But rarely is it as well executed in the excellent production of Trap for a Lonely Man at the Grand Theatre.

If it weren't for the twist, this would have been a fairly routine exercise in deception and double dealing.

In fact, for the first three-quarters of an hour, the main entertainment is deprived by picking holes in what, on the face of it, is a paper thin plot.

But, using another dramatic mainstay, the smoking gun, the action -- which revolves around a desperate man trying to prove that a mysteriously well-informed new arrival at his home in the French Alps is not, as she claims, his missing wife -- moves on with pace, especially after the interval.

It takes a universally excellent cast to provide what is, essentially, a 90 minute deception followed by a five minute (if that) turnaround.

Fortunately, Peter Amory and Sally Ann Matthews in the lead roles deliver, capably supported by Geoffrey Davies and with an excellent turn from Michael Tudor Barnes as a comic-but-pivotal artist/tramp.

Quibbles? Not many. As mentioned before, the early plotting seems thin, but its shortcomings can be forgiven or explained away by the excellent final act.

And it's sometimes difficult to get a sense of place when supposedly French characters speak in the plummiest of English tones -- though, given the choice, this is preferable to any kind of 'Allo Allo' style cod johnny-foreigner accents. That said, a superbly designed set more than makes up for that.

And, occasionally, the tone veers between comedy-drama or out and out thriller with moments of darkly comic humour. That too, is resolved at the end. You'll have to watch the play to find out how!