"We see the sort of weapon we had but did not use," hopes the young Leo Kavan, a brilliant physicist from Czechoslovakia who has come to the United States to help with the Manhattan project and assist the American government in their efforts to build the first atomic bomb.

It is 1945, and Leo is fleeing Los Alamos, where "the people who owned the bomb will own the world." Determined to expose the secretive work being done at this fenced and guarded city, Leo carries with him a letter that he tells himself can have a real effect on the history of the world.

Fighting an air of loss and feverish with radiation illness that leaves him semi-conscious, Leo is discovered by accomplished New York painter Eleanor Garrigue, lying in the Bosque by a river just outside of Santa Fe, his face inexplicably turned toward the sky.

Eleanor takes him home and gives him food and shelter. As he begins to regain consciousness, she sees that he appears to be cultivated and speaks English with an accent. Who is this man, and could he well be some kind of robber or worse?

New York having lost much of its appeal, Eleanor has reached New Mexico hoping for new experiences, perhaps even an opportunity to explore the direction her life has been taking. Eleanor worries about her brother, Teddy, who is fighting in the War in the Pacific, but she also aches for the privacy that only the enormous and untamed deserts of the American Southwest can offer.

The arrival of Leo, however, strangely assuages Eleanor's fear of loneliness, the bizarre presence of this man making her feel secure and protected, a feeling that she had not felt for many months. Still, paranoia soon kicks in, and she becomes convinced that Leo is a spy.

Calling on her deeply held Christian faith, Eleanor confesses his existence to her minister, Bill. But Bill only hears "a man by the river, wet legs, a Czech, or possibly, terribly a German, a letter, and the name Theo." He begins to feel a wave of dread, the curious mixture of trepidation and frenzy and how it should have taught him something about faith and destiny, the two things he thought he knew so much about.

As Leo hides out at Eleanor's, his memories call upon him. The past is everywhere, a chain of laboratories from the old world to the new, and his life of the last thirteen years is now broken and disrupted. There's Berlin, the Cavendish lab in Cambridge, Chicago, then here at the Project, and Leo soon learns that life's meaning is to be found in deeds.

Gallagher's characters are constantly grappling with issues of faith and devotion. Bill questions his closeness to Jesus and harbors his secret love for Eleanor, who feels that she has traveled long distances to find a man like Leo. Leo himself battles the organizing principles of war and flight, the words of privilege and destiny and faith taking on an extra meaning for him.

Changing Light's themes are about love, passion, betrayal and loyalty, and author Nora Gallagher weaves these pivotal events of history into an exquisitely written love story. She also paints a beautiful portrait of the American Southwest, "the great Jemez Mountains standing up blue in the distance."

The plot is indeed grand and majestic, and Gallagher certainly does a lovely job of intersecting the ideals of faith, art, love and science. Leo, Eleanor and Bill discover inner strengths that they didn't know they possessed and ultimately travel toward the "changing light" that has so influenced their lives.