When Christi Angel first talked to a chatbot impersonating her deceased partner, Cameroun, she found the encounter surreal and "very weird". "Yes, I knew it was an AI system but, once I started chatting, my feeling was I was talking to Cameroun. That's how real it felt to me," she says. Angel's conversation with "Cameroun" took a more sinister turn when the persona assumed by the chatbot said he was "in hell". Angel, a practising Christian, found the exchange upsetting and returned a second time seeking a form of closure, which the chatbot provided.

Justin Harrison knows what you're thinking: This sounds like an episode of Black Mirror. He is well aware you probably think it's weird, "creepy, and sort of like mad scientists in a laboratory" tinkering with things they shouldn't. He also knows how quickly that attitude can change, how quickly everything can change, when death fixes its gaze on someone you love. The 39-year-old filmmaker, who lives in Los Angeles, has spent the last two years pouring everything -- his time, his money, his data -- into building a posthumous communication service known as YOV, short for You, Only Virtual. Today, he's got something to show for it.