''Please, dear God, don't let us have killed John Wayne.''
    - Unidentified government official, 1980
   
    Mary Dickson's new play, ''Exposed,'' is a sacrament of grief and anger that doesn't stop at the edge of the stage or end with the actors' bows. Be careful. It gets under the skin and into the marrow, but that's the whole point.
    When I saw it this past weekend in Salt Lake City, where its world-premiere run is sold out, the author and some of the real-life characters the play is based on joined the cast onstage afterward and engaged with the audience - almost no one left, by the way, and those who did left crying - in a fervid discussion of the subject matter: the 928 above- and below-ground nuclear blasts set off at the Nevada Test Site, near Las Vegas, between 1951 and 1992; the devastating effect these tests, many of them very dirty, had on the downwind population; and the government secrecy and lies, as it pursued the Cold War, that kept the public falsely reassured that the fallout that dusted the landscape afterward was perfectly harmless.
    Like I say, I couldn't tell when the play stopped, as art met life in this interchange and the personal stories of the audience members - ''I've had cancer seven times . . . three of my children died of cancer'' - mingled with the storyline of ''Exposed.''
    Dickson, a native of Salt Lake City, an ''accidental playwright,'' as The Salt Lake Tribune described her, has woven three separate stories into this devastating drama that deserves a national audience.
    The first is personal: her own bout with thyroid cancer when she was in her late 20s; her sister, Ann Dickson DeBirk's, losing battle with lupus (she died in 2001 at age 46); Dickson's dawning realization that both of them are ''downwinders''; and her resulting activism, in outraged collaboration with other downwinders, that culminated in early 2007 in the government's cancellation of the proposed subnuclear test blast known as Divine Strake.
    The second story, based on hearing transcripts and Dickson's own interviews, is told in the voices of the downwinders: ''The sheep had burns on their lips and faces from eating grass covered with fallout. . . . Their wool came off in my hands. The government says they died of malnutrition. Hell, they thought we was all dumb sheep herders. But these sheep ate that fallout . . . (and) we sold that wool.''
    ''In 1959, I noticed a hunk of hair and scalp in my brush - I was never well after that. I buy my life now, one month at a time.''
    ''I watched my classmates get sick and die of leukemia. I remember, as a kid, we were given a roll of dimes by a government spokesman who came to our school. He said call us if you see a Russian fighter plane. They were keeping fear alive.''
    Howard Hughes, who felt the walls of his Las Vegas mansion shake and viscerally detested the testing, shows up. So does the cast of ''The Conqueror,'' or at least its memory. The movie, shot in 1955 in the desert near St. George, Utah - in fallout-saturated soil, which permeated the set - was directed by Dick Powell and starred John Wayne, Susan Hayward and Agnes Moorehead, all of whom later died of cancer. As of the mid-'80s, 91 of 220 cast members had contracted cancer and 46 had died of it.
    A 1980 People magazine story on these deaths elicited the above quote about Wayne, the icon, and in ''Exposed,'' as a government official utters it, we hear the cynicism with stabbing clarity. The play's third storyline, personified by two anonymous feds in pinstripes, is gleaned from Atomic Energy Commission transcripts and other sources. The secret high-level debates and public BS wind through the other two stories.
    At one point, as Ann is dying, as the tension is building unbearably, the whole cast, including the G-men, suddenly start singing Bert the Turtle's song, ''Duck and Cover,'' the official civil defense ditty that most baby boomers will surely remember (if you don't, check it out at planbtheatre.org/exposed). The grim seriousness temporarily collapses into nonsense. The effect is astonishing: This is really the level of awareness we had in the 1950s.
    And then it's half a century later. The downwinders have seen countless loved ones die. Many of them have been keeping cancer charts, and marking off the names of their neighbors one by one. When Divine Strake is proposed, they're prepared; they flood the hearings in overwhelming numbers and the government, its power-point disinformation show defeated, cancels the test.
    The storylines converge in a cacophony of irreconcilable differences, each character shouting his or her point of view. Then there's silence, and the play ends with a reading of the names of the downwinder dead. After each show, new names are added.
    The air in the theater reverberated with the reading of those names and, after the discussion, as I left, I was tingling with a sense of outrage, temporary victory and the meaning of participatory democracy.
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    * ROBERT KOEHLER, an award-winning, Chicago-based journalist, is an editor at Tribune Media Services and nationally syndicated writer. You can respond to this column at bkoehler@tribune.com or visit his Web site at commonwonders.com.