The premise is that Nantucket has been tossed back to about 1400 B.C., with the Coast Guard tall ship Eagle in tow just offshore. From this, a new and different time line commences, one complicated by outbreaks of measles and smallpox, the inhabitants' shrewdness, stark treason on the part of one of the time-displaced band, thuggish genius William Walker, and the parallel introductions of diversity and women's rights with those of the steam engine and the ironclad.