By C.S. Gilbert

“Deathtrap” opened Thursday, the final full production in what is arguably Waterfront Playhouse’s strongest season in all its 73-year history. The lauded company — named best professional theater in Florida for the past umpteen years by Florida Magazine — and Danny Weathers, its multi-gifted artistic director, set the bar very high for themselves with the season opener, the howling hit “39 Steps.” Amazingly, subsequent shows maintained or exceeded the high standard —and “Deathtrap” does not disappoint.

The comedy thriller (or thriller comedy?) has a pedigree all its own, reportedly being Broadway’s longest running show of its genre, plus being a play about playwrighting. It first opened in 1978, when technology had developed sufficiently to offer an electric typewriter but the manual typewriter had not yet become a total relic of the past.

Director Bob Bowersox wisely chose not to update the show, which depends in part upon carbon copies (there’s a blast from the past), so it offers a bit of a history lesson as well as a glimpse into the art of formula playwriting. (He could not resist, however, a quick reference to Michael Caine and Christopher Reeve, who created the leading roles on Broadway.) Bowersox is a guest director at the Waterfront; his debut with the company was last season’s “Home Exchange” but he boasts an extensive resume as producer, director and actor. Here he’s damn near perfect.

The cast is superb. But that’s what audiences expect of David Black, Mary Falconer and Mark Watson, who work so well together that one almost suspects they’ve done this one before — which, in differing configurations, they have. All three are marvelous. So, too, is relative newcomer Gene Drum, an imposing figure even before he opens his mouth; he’s a veteran of extensive experience in military theater, amateur and professional, in Bahrain and Saudi Arabia during 29 years in the Middle East.

But it’s Chris Stone as a visiting Dutch psychic who steals the show — and that isn’t easy — with her energy, accent and expertise. And no wonder; she’s been gracing local stages since 1980.

There is, inevitably, one more extraordinary star in this show: Michael Boyer’s set. His décor is nothing less than mind-boggling. The side walls of the writing studio tip in slightly, which, with the sharply contrasting musical interludes between scenes, serves from the very beginning to keep the audience just a bit off-balance and thus more vulnerable for the twists and shocks of the plot. Boyer exceeds himself, which, knowing his years of brilliant design, is barely imaginable. And as technical director of the company, he must be credited for the excellent sound and, with David Bird, lights. The show has an amazingly realistic storm scene.

As always, stage manager Trish Manley keeps things moving along smoothly and Carmen Rodriguez and Leigh Hooten earn praise for props and costumes, respectively.

It’s almost a theater cliché to carp that even professionals often need to pick up the pace of a show. Not these folks — if anything, they could slow down a bit and scream a bit louder during all the thunder and lightning. It’s a shame to let even one quip of this great show get away.

All in all, Waterfront Playhouse and Weathers can bask in the glory of a magnificent season. And it’s not over yet: their series of five special events, brief-running concerts ranging from burlesque to Fiona Malloy and Howard Livingston, will end with a howl as the hilarious Kinsey Sicks, “America’s favorite Dragapella Beauty Shop Quartet,” return at last to help celebrate Key West Pride on June 6, 7 and 8.

Meanwhile, “Deathtrap” earns two Depends for comedy and at least two more for its many moments of shock. Be prepared.