Thrillers and farces are in some ways the hardest plays for critics to review effectively. They don't work the way other plays do - the action is almost totally driven by plot and incident and very little of it by character and nuance, and the play is either effective or not based on the audience's reaction - are they enthralled and thrilled, do they laugh. IF you're going to wax pretentious (and why not, this is a theatre blog with no word limits, pretentious comes with the territory), you could say both are ruthless interrogations on the topic of identity - the difference between the real you and the one you present to the public - and how desperation and desire can change who you appear to be in an instant.
Which is to say that Agatha Christie's "Witness for the Prosecution" is a very, very effective thriller - it does indeed enthrall and thrill, drawing the audience in slowly, casually, with what appears to be a simple courtroom drama of dueling barristers scoring points off each other in the defence of a hapless young man, only to pull surprise revelations out of the hat in the last act in ways that definitely left the audience gasping. There are trails of clues throughout, lightly dusted with several red herrings, and while the ending is surprising there's also a remorseful, horrible logic to how things work out (and aargh, it's kinda annoying that I can't talk about certain plot points in order to say how well they're done, but ... yes, the shocks are very well done).
A reasonably large cast leads us through the action. Our point-of-view character is Sir Wilfred Roberts QC, the barrister charged with defending the young man who may or my not have dunnit, and he delivers with aplomb - slightly pompous, happy to play to the jury's prejudices, yet we never have any doubt that he's doing what he believes is good. Cole Hilder plays his client as a slightly naive and feckless but basically charming young fellow who begins to realise quite how out of his depth he is. Emma Wood shines as his mysterious wife whose motives are continuously up for question - her darting eyes and controlled nature mean we don't miss a nuance. Elsewhere in the cast, there's good support througout - Alice Ferguson as the scottish housekeeper who's a little too eager to point the finger, Morgan Heathwilliams as Sir Wilfred's bubbly secretary, Ian Hart as his equally mordant clerk, Jerry Hearn as the formal but kind-hearted solicitor, Peter Holland as the prosecutor both teasing of his opponent and ruthless in the attack, Jonathan Pearson as a slightly-snooty clerk of court, the trio of David Bennett, Anthony Ives and Brendan Kelly as three very different expert witnesses, and Saban Lloyd Bennett coralling it all with cool formality as the judge.
Aarne Neeme's direction starts a little languid, but keeps the characters and plot engaging enough to keep you going through to the several-layer twist ending. Quentin Mitchell's set looks spectacular and fills the Rep stage admirably. Lighting by Cynthia Jolley-Rodgers subtly keeps the moodiness and deliniates between the warm chambers and starkly-formal courtroom.
This is undoubtedly as traditional as trad theatre gets. But if all trad theatre was like this, there'd be few complaints - it brings the audience in and holds them well with an engrossing tale of murder and its aftermath and keeps then tense till the finale. Go see and enjoy.