"Okay. This has to be a credible threat. Ergo, we have to have seen (and heard about) the real damage Randall has done to Jamie thus far; we have to be in no doubt whatever that he'd do real damage to Claire. We can't just say, "Oh, he's such a nasty person, you wouldn't believe..." We have to believe, and therefore appreciate, just what Jamie is doing when he trades what's left of his life for Claire's."