Started off good then went off the rails
The series seemed to start off good - very atmospheric: eery and ghostly with the past and present blending together. However the fourth episode is where it started to get wonky IMHO with the cliche jump scares and ghosts flying across hallways. Then Episode 5 with the Roundhead ghosts who just showed up yet had never done so before. And if they hung everybody in the village how did they still have a village? Then the last one when they dug up a futuristic car that somehow warped back into their time without a body. They would have been somewhat familiar with "horseless carriages" as they already had trains and the first automobiles by that time. They should have been extremely curious as to what the hell it was and how it got there.
And the problem is the mystery of the woman with the shining book is never really resolved from Nathan's perspective. All he sees is her walking away with his son. And even with her strolling off, she had nothing to do with the other supernatural hauntings going on there that started and ended inexplicably - did the Roundheads come back again on Halloween 1895?
The series didn't seemed to know what it wanted to be. Is supposed to be supernatural or sci-fi or both and were characters supposed to ignore the supernatural or not. Nathan became too readily convinced in the supernatural for his educational background while his skeptical wife had no reason to be skeptical by the time she saw the roundhead ghosts. And why was no one in the village saying "hey, why did all this weird stuff start happening all of a sudden when we never had roundhead ghosts and the like running around before?"
I think the show was trying to be too clever for its own good with all its mysteries. The wrap around story of the great great granddaughter haunting/time slips was interesting and would have worked as its own self-inclusive story but some of the other stories like the Roundheads, the workhouse boys, the murdered girl just seem to come out of left field with no connection to anything.
I think BBC sniffed another Lost in the making with gimmicky mysteries or another shambling Doctor Who Moffat arc that gets so twisted into itself that the mysteries cannot be properly answered in a sensible satisfactorily way because the writer never thought it out completely.
I would have liked to have seen a second series to see if they could have have fleshed it out a bit more or if they were just going to do more of the same spooky spooky without explaining why the past and the present were colliding.