Most of us know Agatha Christie's "Witness for the Prosecution" from the 1957 Billy Wilder film with Charles Laughton, Tyrone Power and Marlene Dietrich. Before that it was a short story that was adapted into a play that opened to rave reviews in 1953 in London. The story of a prominent attorney defending a personable young drifter accused of murdering a rich old widow is gripping on its face, and it's augmented by a classic Christie twist on which everything hangs.

Most of us know Agatha Christie's "Witness for the Prosecution" from the 1957 Billy Wilder film with Charles Laughton, Tyrone Power and Marlene Dietrich. Before that it was a short story that was adapted into a play that opened to rave reviews in 1953 in London. The story of a prominent attorney defending a personable young drifter accused of murdering a rich old widow is gripping on its face, and it's augmented by a classic Christie twist on which everything hangs.

In Oregon Stage Works' new production of the old warhorse, which premiered Thursday night in Ashland, directed by Lisa Marie Wingbermuehle, the redoubtable Brian Wallace plays legal eagle Sir Wilfrid. Dayvin Turchiano is drifter Leonard Vole. Jennifer Miller-Brian plays Romaine, Vole's presumed wife.

When Vole is accused of bumping off the old lady, it looks bad. He's unemployed and needs money. He befriended the old lady and visited her often. Without his wife. And it turns out she'd recently changed her will to leave him everything.

But the likable Vole seems to Sir Wilfrid — and us — a victim of circumstances and his own naivete. Surely no self-respecting murderer-for-money would be so careless, so indifferent to appearances. Sir Wilfrid, assisted by Mayhew (Joe Charter), is drawn to the case.

Things heat up when Romaine, who confirmed Vole's alibi in Sir Wilfrid's office, saying that Vole came home before the murder, changes her story in court and becomes what the title says. It now seems Vole came home after the murder, with blood on his jacket to boot.

Both Vole and the old lady are type O, so whose blood is it? What a difference a half-century makes; Wingbermuehle and Wallace have set the play in October of 1955, long before DNA evidence.

A melodrama is a change of pace for OSW, which is known for staging headier stuff. But a courtroom drama automatically has some things going for it. Something crucial is at stake in the outcome. Every point is charged with significance. The adversarial proceedings guarantee conflict.

On the downside, not much actually happens in front of us. Rather, stuff from the past comes out in courtroom exchanges. Each of the two acts opens in Sir Wilfrid's chambers, then jumps to the Old Bailey Court Room.

When Sir Wilfrid goes up against prosecutor Myers (Joel Handley), the court becomes a boxing ring, with Sir Wilfrid as a cagey old Muhammad Ali type looking for one more stroke of magic, and Myers as the confident challenger. These scenes generate some electricity, but a few big moments could have used more juice.

Rochelle Savitt has a delightful turn as Janet MacKenzie, the old lady's bitter maid, who hates Vole and must be brought down by the resourceful Sir Wilfrid.

Wallace, who co-directed and also designed the set, is generally believable as the droll, upper-crusty Sir Wilfrid, although his focus seemed to drift a bit at times. After all, Laughton ran away with the film.

Turchiano's Vole is an open-faced, working-class bloke who quickly inspires our trust. Miller-Brian's Romaine is a grasping harpy whose machinations are key to the entire melodrama. Handley is relentless as the foe who desperately wants to bring Sir Wilfrid down.

Wingbermuehle, a founder of the Student Production Association at Lane Community College in Eugene a few years ago, moved to Ashland in 2005 to attend Southern Oregon University and has stage managed at OSW. "Witness" is her directing effort at OSW. It's stylish, and brisk enough, even if one would like to see more heat in the hot parts, and a little more cool in the stuff in between.

Christie's genius plot twist near the end is nicely staged, and it's followed by one final surprise. "Witness" proves a play needn't be deep to be engrossing. We all gotta know whodunit.