The Sisters of Sin are the leaders of a quasi-religious cult that promotes hatred and violence. Led by the enigmatic Mother Night, the Sisters prey on unsuspecting teenagers, inoculating them with their venomous dogma through a variety of brutal mind-control techniques. While the origins of Mother Night herself remain unknown, her lieutenant Sisters are known to have previously been disciples of the Red Skull, who guided the creation of the original Sisters of Sin. In fact, the sister known as Sin is in actuality the Red Skull's daughter. After having spent years indoctrinating his daughter into his own twisted philosophies, the Skull then accelerated her aging process artificially, hurling her headlong into adulthood. He then bestowed upon her the name of Mother Superior, and gave her charge of four young orphan girls who were in turn indoctrinated by Mother Superior. Once this was done, the Skull brought each of the girls to premature adulthood as well, experimenting on each in the process to give each one a particular talent. Thus were formed Mother Superior and her Sisters of Sin. However, after the Skull's death resulted from a clash with Captain America, Mother Superior and the Sisters were restored to their rightful ages. Apparently, this process allowed them to retain at least part of their artificially enhanced abilities. Through an as yet unknown series of circumstances, they were discovered by the mysterious Mother Night, who was formerly known as Suprema, and who organized them into the second Sisters of Sin. The full story of how this transpired has yet to be told.

Bernadette Rosenthal, an old girlfriend of Steve Rogers, called him to say that she was worried about her youngest sister Nancy who had run away from home. Rogers checked around and found that an unusually large number of child disappearances had been going on lately and decided to investigate the matter personally. He would need a disguise though and enlisted the aid of his teammate Sersi in transforming him into a 15-year old version of himself. Then, pretending to be a teen runaway, he was picked up by two of the Sisters of Sin and was knocked out by Sister Raunch who used her mental powers. When he regained consciousness, he found himself going to Mother Night's youth training camp where, aided by the Sisters of Sin, she was training young runaways to hate and kill.

Rogers and the other "recruits" were off-loaded from the bus and put in holding cells about the size of closets. One of the other kids, a girl named Jennifer, had claustrophobia and when she put up a fuss, Sister Sin proceeded to beat her. Rogers tried to intervene but found his teen body incapable of handling the combat moves of his adult self. Later that night, Rogers managed to escape and he broke Jennifer out as well. They made their way to the main house looking for a phone, but were captured by Sister Sin instead. Sister Sin beat Rogers senseless and discovered that he was wearing a Captain America suit under his clothes. When he awoke, Rogers found his street clothes had been removed leaving him in his Captain America costume. He pretended to be a member of his own computer network (Stars and Stripes), but Mother Night nonetheless decided to have the Sisters of Sin beat him to death.

Luckily for Captain America, Sersi had conditioned the transformation so that it would automatically reverse itself if he took more than 40 punches. Just as the Sisters of Sin closed in on him, he suddenly reverted to his adult self and was able to take care of the Sisters of Sin with no difficulty. Ultimately, the Sisters of Sin escaped, although Mother Night was captured.