Cassandra Cain has a twin sister she never told anyone because her sister never escaped her father and his training, his expectations so she thought her sister was dead. She thought wrong. So when people all across the globe in Gotham, in Metropolis and so on start dying in mysterious ways or disappearing entirely, but the Batfamily knows where David Cain is and it's not him murdering people. But Cass knows that only one person could be doing this. You her twin sister who she thought was dead for the past ten years or more.