In 1921, Sarah Clarke was going to die. She had long ago accepted that fact but there was another plan for her. She was infected with the B-43C virus, otherwise known as the guardian-making virus. After decades of training, she was assigned to Luca James. After 6 months, they fell in love and became engaged. However, the next year, Luca was killed in front of Sarah. She had a breakdown and was taken out of the field for 56 years. After a guardian is killed, she is put back into the field, where she is assigned to Connor Duncan. Soon, she falls in love with Connor but she's torn between her guilt over forgetting Luca and her all-consuming love for Connor. But what she doesn't know is that someone is hunting Sarah and being in love with Connor is threatening both their lives. So the race is on to find the killer before he finds them.