Y/n grew up idolizing her older brother, Steve Rogers. She never expected to fall in love with his best friend, Bucky Barnes. And she definitely never expected Tony Stark to become the overprotective father figure who insists on giving Bucky “the talk.” Everything feels almost normal—until an old HYDRA file reveals Y/n was experimented on as a child, and the dormant programming inside her is beginning to awaken. Now Steve will do anything to save his little sister. Bucky refuses to lose the woman he loves. And Tony is prepared to burn every HYDRA base to the ground before they can take his kid away again.