Mark of Cain & Thrillkill are both Canadian films from the mid-80's, and they're both worth a watch if you're a fan of 80's horror flicks, but don't expect anything spectacular. Both films are rather gloomy & almost claustrophobic in their atmosphere. Mark of Cain is about identical twins, one of whom is locked up in an asylum for nailing a neighbor to a tree. When the sane one announces he's selling their old house because he's strapped for cash, the insane one once again demonstrates why he's locked up by escaping and coming back home.
Thrillkill is about a video game developer who uses her talent to clean out the financial assets of many large companies, and she was to be sharing these proceeds with partners, although she decides that maybe she'd like it all for herself, which gets her killed and leaves her partners after her sister to find where she stashed the loot. Thrillkill is actually the more interesting of the two films, because more and more mysterious perps keep showing up till you're not really sure who is a good guy & who is not. And Thrillkill gives you more bad 80's fashions and big hair, too.
Neither film is anything to drool over. They're just OK films, worth watching if you're in the mood for something gloomy, Canadian, & 80's.