Shear Madness bills itself as the longest-running play in U.S. history (since 1980), and you don’t get to that level of popularity without offering something for everyone. Here, that something is a fairly generic, inoffensive mélange of whodunit and Whose Line Is It, Anyway? It’s an audience-participation show, partly improvised in response, meaning that your enjoyment will be directly proportional to the involvement—or lack thereof—of those seated around you. The plot makes the board game Clue look like a John Grisham novel; with blanks we must fill in like a crossword puzzle, the results are often fun, but rarely funny.

There’s been a murder in an apartment above the Shear Madness salon, and only one of those present in the shop when the mystery opens could be the killer. Who it will be depends largely on audience vote; the show has multiple endings to accommodate any potential assailant.

Taken as an amusement in the dinner- theater/murder-mystery vein, Shear Madness is all well and good, but the creators double down on dumbing down. This traveling production leaves openings throughout the text where the visiting troupe can insert witty regional asides about, say, Tukwila, Starbucks, or the Sonics. (The program even lists the salon’s location as Capitol Hill.) As at Applebee’s, there really is something for everyone here. Trouble is, none of it’s very appetizing.

Shear Madness began life as a more conventional German murder mystery called Scherenschnitt (by Paul Pörtner). What Bruce Jordan and Marilyn Abrams added is a sketch-comedy/improv approach that keeps the show chugging forward in search of yucks. And because the performers are often trying to crack one another up, there’s a good-natured bonhomie that entertains even when the jokes fall flat.

Among the cast, Mary Ann Conk seems to be having a particular blast with her Lily Tomlin–inspired take on hairdresser Barbara. Joe Ditmyer turns the smarm/charm up to 11 to play “used antiques dealer” Eddie (with more than a passing resemblance to John Edwards). Patrick Noonan holds the show together as head interrogator Nick.

There are so many gimmicks, and the show tries so hard, that Shear Madness could safely entertain several busloads from the old folks’ home without fear of heart attacks. But watching it, I kept remembering what someone once told me about Quentin Tarantino movies: “They’re both good and original. Unfortunately, that which is good isn’t original, and that which is original isn’t good.”