Zero Day' star Lizzy Caplan on that huge finale twist, sparring with Robert De Niro, what Jesse Plemons' Roger means to Alex and 'Mean Girls.'

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.

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