After three episodes, I'm done
I was not crazy about the first episode of Mercy Street, but I was willing to stick with it for at least two more episodes to see if it improved.
IMO it has not. While the series is not awful, it's pitched at the "Law and Order SVU" level -- every character trait and every plot development is made painfully obvious. That could be a good thing if you like to surf the net while watching TV. But if you're expecting a program that commands your attention (as Downton Abbey often does), MS is not it.
*****
"Walt is a racist, moronic, troll. Ignore his stupid ass." -- I_Destroy_Stalkers