The one thing you can be sure of when you settle down to watch a thriller is that the first conclusion you come to is guaranteed to be wrong.
And so it is in Strictly Murder by Brian Clemens, running at The Courtyard until Saturday.
Set in a pre-mobile phone world, when it was possible simply to change your name and go to ground, when an ATM or GPS wouldn't give you away and you could reinvent yourself and build a new life, Strictly Murder opens in an isolated cottage deep in Provence where Suzy and Peter happily scrape a living from his painting and her job in the local hotel.
But when the very dapper Frederick Moss (Brian Capron), a Scotland Yard detective knocks on the door, it's clear that nothing is what it seems. And what's to be made of Josef, the 'addled' neighbour who is either skulking around the couple's home or standing guard on a nearby hilltop, gun always at the ready? And who is Giles Hudson? When death comes calling, it's obvious what and who is guilty and of what, and why ... or is it.
After a slow burning start, the surprises come thick and fast and the second half confounds every assumption about guilt and innocence, all set against a menacing background of impending war as the radio on the dresser intermittently issues crackling broadcasts from Chamberlain and Hitler.
Strictly Murder is a thriller set firmly in the past, an old-fashioned, charming, but still surprising, drama that relies on ingenious plotting rather than technological wizardry - where an oil lamp set in a window is the most sophisticated way to signal danger.
Brian Capron is clearly having a ball playing Moss, a performance suggesting the odd nod in the direction of David Suchet's Poirot, while Gary Turner gives Peter Meredith the level of ambiguity the character needs to keep the audience guessing. The cast is completed by Lara Lemon as Suzy, Corinne Wicks as Miriam Miller and Andrew Fettes as Josef.
Lovers of whodunnits and whydunnits will undoubtedly be satisfied with a thriller with the kind of unexpected ending they expect and plenty of twists and turns along the way.
Strictly Murder runs at The Courtyard until Saturday. To book, call the box office on 01432 340555 or visit courtyard.org.uk