“The [Ebola] monster is so scary because it is not only invisible, you can’t combat it,” says Topher Grace (standing, right), here with his fellow cast members: (seated) Julianna Margulies and Liam Cunningham and (standing) Paul James, Noah Emmerich and James D’Arcy. Fortunately for the world — and viewers — The Hot Zone ends on a hopeful note.