The story of Michael Frayn's Copenhagen, which opened last night at the Royale Theatre, is simple. In 1941 the German physicist Werner Heisenberg made a trip to Copenhagen to see his Danish counterpart and mentor, Niels Bohr. (They had revolutionized atomic physics in the 20s with their work on quantum mechanics and the uncertainty principle.) Exactly why Heisenberg sought out Bohr, old friend and colleague but now an enemy in the middle of a World War, has never been satisfactorily explained. Frayn's Copenhagen speculates on plausible reasons in this the season's most intellectually stimulating and emotionally satisfying play.

As befitting the author of the split-second comedy Noises Off, Copenhagen's three characters - Werner Heisenberg (Michael Cumpsty), Neils Bohr (Philip Bosco), and Margrethe Bohr (Blair Brown) - lead us through round after bravura round of "what ifs," in an attempt to explain to themselves, as well as to us, what may, what could, what probably did happen during that fateful meeting, and, more to the point, what it all means in very human terms.

Science, even brilliant science, does not define an age. It's what human beings do with it, and the effect it has on them, that matters. For all the offered, simplified explanations of the science at the core of Copenhagen, it's the story of these three people, Werner, Neils and Margrethe, that touches you and which you will remember long after the lucid but secondary examples and applications of the uncertainty principle have ceased to trouble your mind.

Michael Cumpsty and Philip Bosco are giving the performances of their impressive careers in this play. Cumpsty, all tightly wound nerves, apprehension, fear, anger, and ego is the perfect foil for Bosco's grand old man of science; both hesitantly seeking to reestablish a lost camaraderie and understanding. Blair Brown, as the watchful, protective wife, gives a performance subtle at first, but rich in detail and powerfully nuanced.

Michael Blakemore's direction is almost lyrical in its effective use of movement. Peter J. Davison's massive and towering set is an intimidating echo of the brutalist architecture popular in Europe for the last half century. Mark Henderson and Michael Lincoln's lighting expertly underscores the play's shifts in time and place. Only Charlotte Bird's costumes strike a false note, far too modern in cut and fabric for the period.

Copenhagen by Michael Frayn. Directed by Michael Blakemore. Starring Philip Bosco, Blair Brown, and Michael Cumpsty. Designed by Peter J. Davison. Lighting designed by Mark Henderson and Michael Lincoln. Costume supervision by Charlotte Bird. Sound by Tony Meola.

Theatre: Royale Theatre, 242 West 45th Street (between Broadway and 8th Avenue)

Running time: 2 hours and 25 minutes, including one 15 minute intermission

Schedule: Tuesday through Saturday at 8 PM, Wednesday and Saturday at 2 PM, Sunday at 3 PM. Warning: Latecomers are not seated until intermission, which is approximately 70 minutes into the performance.

Audience: May be inappropriate for ages 15 and younger. Children under 4 are not permitted into the theatre.

Ticket prices: $65, $60 and $50 (Seats on the stage are sold at the Box Office only.)

Student Rush Tickets: $25 Student Rush tickets are available at the Box Office only, on the day of performance. A valid student ID is required. Limit 2 per person, subject to availability.

Tickets online: TeleCharge

Tickets by phone: TeleCharge at (212) 239-6200, or outside the New York metro area (800) 545-2559, 24 hours a day, 7 days a week

Tickets in person: Box Office hours Monday through Saturday 10 AM to 8 PM, Sunday Noon to 6 PM

Tickets by E-mail: tickets@telecharge.com

Tickets by Snail mail: Copenhagen, PO Box 998, Times Square Station, New York, NY 10108-0998