Sibling Dread

A boy and his half-sister were imprisoned for numerous murders. They were so young the authorities had to place them in a secure unit for underage killers. A woman with devilish plans busts them out, she needs their unusual skills. Trouble starts as soon as they are freed. In another part of the country, a woman cares for the boy, she needs to track him down. Is his sister a vampire? This story is set in Thailand, where they have their own monster to match the West's vampire.