At one end of the city sits the old U.S. Naval Observatory, its scientists plagued by river fog, malaria, and chronically short funds. There, in the spring of 1877, Hugh Allison, a handsome, mischievous researcher, remains oblivious to all but his own secret scheme to project an image through time and space.

Into his orbit comes Cynthia May, a beautiful but care-ravaged war widow. After a dozen years of impoverished drift through the city's boarding houses and clerkships, she seizes a chance to put her freakish skill with numbers to work as one of the Observatory's "computers." She soon finds herself in love with the younger Hugh Allison, because -- and despite of -- his merry dispensation from the Civil War that has haunted her life.

The fate of their love affair and Hugh's heavenly vision may lie not inside the Observatory but across the city, in the parlor of an astrologer and on Capital Hill, where the Senate -- convulsed by Reconstruction, Indian wars, "reform" and a wildly disputed presidential election -- is ruled by its cruel spellbinder, Roscoe Conkling of New York, a figure as dangerous as he is magnetic.

In Two Moons, Mallon combines scrupulous historic detail and startling invention into a thrilling story of heartbreak and last-minute otherworldly triumph.