by Clarke Groome

The Walnut Street Theatre’s often very funny production of “The 39 Steps” is based on a John Buchan novel that became an early Alfred Hitchcock film. (“Hitch” is seen here with one of his more adoring fans.)

It is often very funny. There are times, however, when the Walnut Street Theatre’s production of “The 39 Steps” seems more about the shtick than the story.

In Patrick Barlow’s adaptation of the John Buchan novel that became an early Alfred Hitchcock film, this “The 39 Steps,” which had successful runs in London and New York, uses four actors to play dozens of roles. They all serve a slight story about Richard Hannay (David Hess) becoming an unwitting player in a spy plot that takes him from London to Scotland and back again. Along the way he is accused of murder, absconded by Bobbies who aren’t really coppers and handcuffed to an innocent lady. He ultimately solves the mystery, as one would expect in a Hitchcock thriller.

The original concept of having four actors play all the characters and of playing up the laughs at the expense of the mystery is, in theory (and apparently to many in New York and London), a good idea. I concur.

The problem with it, at least in director William Roudebush’s enthusiastic production at the Walnut, is that it never lets up. It’s one slapstick thing after another.

Some of them — like the references to other Hitchcock movies, “Psycho,” “The Birds,” “North by Northwest” and “Rear Window,” and the appearance of Hitch in a cameo, as he always did in his movies — work really well.

Others, like the overdoing of some silly accent business and the exaggerated walk when one of the two men who play most of the parts also becomes the matron of a Scottish inn, don’t.

Roudebush is a good director. His cast — David Hess as Hannay, Joan Hess as all the real women in the piece and Paul Riopelle and Dan Hodge as everyone else — is up to the challenges the piece places on them.

They are all well supported by designers Robert Andrew Kovach (sets), Paul Black (the intricate lighting), Colleen Grady (costumes) and Christopher Colucci (sound).

Some in the audience were clearly more tolerant of all the silliness than I. While I really admired a lot of the Walnut Street’s “The 39 Steps,” I wish there had been less of it.

For tickets to the Walnut Street Theatre’s production of “The 39 Steps,” which plays through May 1, call 215-574-3550 or 800-982-2787 or visit www.walnutstreettheatre.org