It's a cerebral play that — in the TAG production — struggles and fails to engage audience emotion. Without that essential emotional connection, the drama becomes heavy water we relentlessly sink in.

Externally, the script is exceedingly sparse — a blank stage with three chairs. The characters speak the playwright's blend of history and fiction in dialogue that mixes personality with philosophy and politics. They exist in an unreal dimension, as if reviewing their actions from beyond the grave.

At its center, the issue concerns nuclear fission — splitting the atom. Imagine shooting a neutron bullet into a sphere of compacted marbles (the uranium atom). The marbles scatter, creating a runaway reaction. Applied to the uranium atom, the result is a nuclear explosion —the atomic bomb.

During World War II, the Germans were searching for the key to nuclear fission. Leading that search was Werner Heisenberg, a "white Jew." In 1941, he traveled to Copenhagen, then occupied by Germany, to visit with Niels Bohr, his former teacher, mentor and father figure.

The course of their discussion becomes the center of the drama and an enigma of speculation. What they said to each other is the mystery that drives the play.

"Copenhagen" won a Tony award for best play in 2000 and has been made into a television movie.

But the TAG production doesn't fire the right neutron bullet to initiate a dramatic chain reaction among the characters.

The first act is static, and even the looming mushroom cloud of a nuclear explosion painted on the back wall doesn't keep us focused on the central threat of uncontrolled chaos.

Frankie Enos turns in a controlled but single-note performance as Bohr's wife Margrethe. Richard MacPherson is similarly one-dimensional as he articulates Heisenberg's earnest passion.

David Schaeffer directs and plays the more complex role of Bohr. But none of the references to Heisenberg's "shy schoolboy smile" and the obvious parent-son connection between the two men are able to create interesting interpersonal dynamics.

One might expect an impassioned debate of ethics and morality between two flawed and all-too-human intellectuals. Act 1 must pull us inexorably into Act 2.