An Act of the Imagination by Bernard Slade, directed by Kathryn D. Beall, is, typical of British mysteries, a many-layered story peopled with eccentric characters and featuring surprise twists - in this case, multiple surprise twists.

Arthur Putnam (John Pratt) is a successful mystery writer in London. The time is 1964, which is made clear by the terrific period costumes by Allison Gerst - the bell bottoms and colorful jackets worn by Arthur's son, Simon (Wyatt Wilson), the smart business atire worn by his editor, Holly (Rasaja Hart), and the wild hippy clothes sported by Brenda (Sabrina Husseini).

Arthur's latest novel is quite different than any of his earlier works. Among other things, it describes in graphic sexual terms the affair of his married protagonist and a younger woman. Arthur's wife, Julia (Rhoni Lozier), and his son, Simon, are surprised that he can even imagine such explicit sexuality - Julia is particularly taken aback because she knows Arthur has shown little or no interest in sex in years. In fact, she can't remember him ever being very ardent.

And then Brenda shows up. A '60s go-go girl with a squeeky voice that made it hard for me to understand everything she said, but her body language made clear what I could not hear. Brenda confesses that she is the model for the girl in the novel and that she and Arthur have been having a torrid affair. She demands a payoff from Julia for her silence.

It is not until the end of the first act that the audience is aware that there is a mystery afoot. Someone goes missing, and there is blood and an abundance of evidence, but no body. From this point forward, An Act of the Imagination becomes a classic whodunit with one unexpected twist after another.

Pratt is totally believable as the mystery writer. His acting is subdued. If it were not such much in keeping with his character, I would have thought he was having trouble remembering lines during some akward pauses, but that was simply Pratt being convincingly Arthur. I've seen him in many heavy dramas, most notably Educating Rita and Oleanna, and if this is not one of his best performances it is at least right up there with the best.

Also turning in some top-notch acting are Tom Lockhart as Detective Sergeant Fred Burchitt and Husseini in the dual roles of Brenda and Brooke Carmicheal. Local theater patrons might remember her playing Maria in West Side Story as a child actor at Capital Playhouse. She's grown up, and is now a freshman at Pacific Lutheran University. In An Act of the Imagination, she successfully pulls off the difficult feat of playing two very different characters. Wilson seems a little awkward, working too hard to be Simon. He is a young actor with, I gather, limited experience outside of high school and college productions, and will probably develop into a fine actor with more a few more shows under his belt.

If you enjoy quirky classic British mysteries, you'll surely enjoy this one.

An Act of the Imagination, 7:25 p.m., Thursday-Saturday; and 1:55 p.m., Sunday, through Oct. 30, Olympia Little Theatre, 1925 Miller Ave. NE, Olympia, tickets $9-13, available at Yenney Music, 2703 Capital Mall Dr., Olympia, 360.786.9484, olympialittletheater.org