For Kivrin Engle, preparing an on-site study of one of the deadliest eras in humanity's history was as simple as receiving inoculations against the diseases of the fourteenth century and inventing an alibi for a woman traveling alone. For her instructors in the twenty-first century, it meant painstaking calculations and careful monitoring of the rendezvous location where Kivrin would be received. But a crisis strangely linking past and future strands Kivrin in a bygone age as her fellows try desperately to rescue her. In a time of superstition and fear, Kivrin – barely of age herself – finds she has become an unlikely angel of hope during one of history's darkest hours.