In the second episode of new TV drama, “It’s a Sin,” a young woman named Jill comes to check on a friend who’s been unwell. “Just keep your distance!”, he blurts as he opens the door, then jumps back six feet — leaving her hanging awkwardly in his doorway. Before long, she’s running his errands and dropping off groceries on the doorstep. But each time she returns to her own apartment, the viewer sees Jill scrub frantically in the shower, scouring herself to purge the taint of the infected household.