“Saturday Night Massacre” feels more like a penultimate episode rather than a regular one. With only ten episodes per season, we are inching closer to the fourth season finale, and if “Saturday Night Massacre” is any indication, more lives will be lost before any headway is made. Lexi (Scarlett Byrne) emerges from her cocoon, and while she still looks the same, she isn’t. Lexi’s powers have magnified exponentially and she’s chosen her Espheni family over her human family.