Jack is a retired assassin/spy from the DDSY. He used to be part of the Guardians, but after getting shot in the head and almost dying, he left saying how he had so much he still wanted to see. Years after his retirement, the Guardians come back and tell them they need his help. They tell his a crazy contract killer is after them hunting them one by one, and she is responsible for the death of Sandy. He reluctantly agrees to help them, and starts tracking this killer down. Jack didn't anticipate the past of the killers, and the motives behind the assassinations. They eventually get him thinking who is he working for, and who the real good guys are.
Elsa has had a rather unfortunate past. She was a past DDSY assassin/spy, a former KGB agent, and a member of the Guardians. She was a strong minded woman, but there was only so much she could take. After her eyes were opened to what she was doing, she left and went off on her own wanting nothing but revenge. The urge to kill people is now engrained in her mind, so she became a contract killer, and one by one hunts and kills those who are responsible for ruining her life.
When she captures a past Guardian, and uses him for a torture toy she finds him different than the others, and finds herself growing attached. After an incident happens to her sister she finds herself needing him even more, because she is now faced with a challenge she never thought would happen to her again.