When Doctor Annia 4424 first isolated the dormant retrovirus, she thought she had uncovered a harmless fragment of DNA. By the time she realized what she had really found, her discovery had triggered an alarm. Century Plague was so virulent it had twice threatened to wipe out galactic civilization, and even to study it in simulation carried a Federation death sentence. But Annia knows something no one else does. The virus wasn't eradicated with the firebombing of the infected worlds. It is programmed to come out of dormancy and spread again across a defenseless galaxy. When Guardian is attacked by the Commonwealth, Annia flees the ship with help from two clone soldiers. Together, the three strangers find sanctuary on the United Worlds frontier planet Yetfurther. However, when Annia resumes her study of the virus, she realizes she has miscalculated when the plague would reemerge. The virus is on an accelerated schedule, and time to engineer a cure has already run out.