Sometimes an actor's mettle is tested not by the stretching he has to do to serve a director or a script, but by some unexpected event. A medical emergency developed in the audience at Friday's opening night performance of "A Steady Rain," which caused a short but worrisome delay in the regional premiere of Keith Huff's one-act drama at the Guthrie Theater in Minneapolis.

A young patron seemed to be having a seizure. Fanned by fellow patrons and attended by theater staff, he recovered enough to leave under his own power and was applauded, like an injured athlete, as he walked out of the theater.

Returning to the stage, actors Thomas Vincent Kelly and Sal Viscuso, who were so attuned to the distressed patron that they recognized the situation long before most members of the audience caught on, kicked everything back into high gear.

They used the momentum-breaking interruption as fuel for their fire, delivering with such muscularity and passion that it turned a performance that was already gripping into something much more potent and memorable.

Kelly and Viscuso are the only cast members in Huff's tough Chicago-set police drama about love and the law. They play lawmen who are white ethnics in a great American city that also has a history of corruption and notorious crime. Kelly depicts Irish-American cop Joey, a single guy with a weakness for alcohol and a secret crush on Denny's wife, Connie. Joey mostly does things by the book, even if Denny mocks him for taking classes on racial tolerance.

Viscuso plays Denny, a married Italian-American father who supplements his beat-cop income with side gigs that would surprise both Connie and his supervisors. Denny, who has a thing for a particular prostitute on his beat, can't let go of his deep-seated ideas about race and gender.

The two men grew up as best friends and non-blood brothers, with one dominating the other. But their lives have been diverging for a while. Now, after an encounter with a serial killer on their beat gets them in hot water, their rivalry becomes life-and-death.

In many ways, "Rain" is very much like a one-person production. It is more told than enacted. But with two people, director Jeff Perry (a co-founder of Steppenwolf Theatre and a regular on TV's "Scandal") has more ways to amp up the tension.

On Broadway, Daniel Craig played Joey and Hugh Jackman played Denny. I can't imagine they were any better than Kelly and Viscuso. The two men in Minneapolis are like sparring partners in some moments, dance partners in others. They have great chemistry as they use their bodies to show us, in the slit of their eyes or their sideway glances — in their loud silences and in their sizing up of each other — how best friends become something else.

The two actors take us into the minds and hearts of their characters. We may not agree with them, but we see their points of view clearly, and the logic that they follow.

The producers of "Rain" — the show is a co-production with L.A.'s Odyssey Theatre Ensemble — didn't spend much on design (which is not a bad thing). The set, by Adam Fleming, consists of two swivel chairs and some projection screens that are used to suggest moods and locales. Michael Gend did the moody lighting.

This minimalist design gives actors Kelly and Viscuso the necessary space to show us their skill. The two men conjure not only their characters, but a world for us. They perform with winning empathy and clear skill.

Rohan Preston • 612-673-4390