Is the Sin Eater a plot device? It's debatable. On the one hand, he did appear at just the right moment and solve the mega problem of the series which is that Ichabod and the Headless Horseman are connected via blood. That's pretty "god from machine" to me. But on the other hand, I do believe the Sin Eater will play a bigger role in the series, whatever that might be (one does not hire John Noble for just one episode. Especially when the creators of this show worked with him for 5 years previously, creating one of the most beloved cult show characters). But I'm getting ahead of myself.
--I didn't want to ship Ichabbie but I think I'm a goner. Between Ichabod bowing to Abbie in the beginning and then them hugging at the end, let your ship flags fly.
--I fail to see why they brought Jenny back into this episode. She didn't actually do anything; Abbie figured out where the Sin Eater was.
--The episode ended with the Horseman going to Ichabod's underground cave/grave. Does he sense that the two are no longer tied? Will we see the other Horseman? We've already seen Pestilence.