Netflix's show Zero Day, starring Robert De Niro and Jesse Plemons, depicts a frightening possibility. What is a zero day and could it happen in real life?

Let's break down the explosive series finale of Netflix's "Zero Day," a cautionary tale about autocracy, misinformation and cyberterrorism.

For Lizzy Caplan, joining Netflix's "Zero Day" was an easy decision to make, citing Robert De Niro's involvement, as well as the "solid" credentials of co-creators Eric Newman, Noah Oppenheim and Michael Schmidt.