Few stories on stage have characters that are irredeemably evil. Most drama is about exploring why people do the things they do, building connections and empathy.

In “One Flew Over the Cuckoo’s Nest,” that rule is broken in the character of Nurse Ratched who is sadistic, cruel, power-hungry and, yes, evil. In What A Do Theatre’s production of the Dale Wasserman play (based on Ken Kesey’s novel), Lesley Shabala is creepily perfect in her portrayal of the iron-fisted nurse whose cruelty ranges from absurdly amusing to deadly.

Her every move is contained and controlled, and she owns the stage whenever she is on it. She often says as much with a pointed glare as she does with her words.

Shabala’s Ratched rules over the ward of a mental institution, claiming to establish her rules and policies for the good of the men being treated there and in the interest of “therapeutic community.” Her so-called benevolence is called into question by the arrival of Randall McMurphy, played by Joe Dely. McMurphy is in the ward to dodge a prison sentence work party as he’s decided that pretending to be insane will get him a cushier sentence than working a farm.

To Dely’s con man, everything is a game and he quickly calls Ratched’s behavior for what it is – abuse. But to him it is a game. He decides he will make her crack, and gets the other inmates to bet on whether he can get her to lose her cool within a week’s time.

Dely imbues McMurphy with great charisma and energy. He and Shabala are divine foils, clashing in what becomes an epic battle for human dignity, control and community.

Given how much the state of mental health care has changed in the past 40 years since this story was first written, its relevancy would be questionable if it were not for the meaning transcending its setting and specific situation. The patients help show that the battle isn’t simply over how mental health care should be administered, but about how those in power treat the vulnerable and the amount of power that we give to the cruel out of fear, insecurity or the desire to have what they have, be it confidence, strength or power.

Dave Stubbs’ Harding displays this vulnerability as he swings from the would-be alpha male who has the greatest intellectual grasp on their situation to the cringing, emasculated victim who lifts not a hand in his own defense when Ratched sets his fellow patients against him. He also provides the crucial narration that explains how Ratched has achieved such power, power that goes far beyond what is granted to her institutionally. He tries to explain to McMurphy that he and the fellow patients are bunnies, helpless victims to the cruelty of the world and easy targets for both dedicated sadists and those who are carelessly cruel.

Directed by Randy Wolfe, the patients are an ensemble of crazies, each unable to function in society and progressively weakening until the arrival of McMurphy. Josh Olgine puts in a powerful performance as Chief Bromden and commits to an arc of character development, the one who is most affected by McMurphy, though only Nicolas Mumma’s Martini remains unchanged by the convict’s presence. Ian Russell’s Billy stutters and shakes his way through the show, having his moment of brilliance in the second act where it seems that perhaps all will yet be well.

Like most What A Do performances, this production takes advantage of their superior light system, with Cory Kalkowski’s intricate design that includes black lighting, flashing lights from the nursing station and the sterile, stark bright white light of an institution.

Of special note in this production is Olgine’s set design. The walls of the institution contain paintings representing his character’s hallucinations, paintings that show up only under black lighting when Chief Bromden gives his shock-treatment induced monologues.

This production again features original music composed by John Purchase, a frequent contributor to What A Do’s productions. The music serves as eerie scene transitions, never letting the audience forget the precarious mental balance of those on the stage or what is at stake in the battle between McMurphy and Ratched.

Wolfe carefully manages every moment, and keeps the action moving across What A Do’s wide stage. The two-and-a-half-hour show moves quickly, and the climax and resolution are both so powerful that the audience is left drained and emotionally wrung afterward.

“One Flew Over the Cuckoo’s Nest” tosses down the gauntlet, asking how we care for the weak and vulnerable and what is within our ability to empower or further victimize them. While there may be few Nurse Ratcheds in the world, their existence is made possible and they thrive when others give them power or stand by and watch as they victimize others. Challenging them often comes at great personal cost, and may even seem like impossible odds, but McMurphy’s final contribution isn’t measured in whether he succeeded or failed, but in the difference he made in helping the few move from victim to survivor.