Spoiler alert: Do not read on if you have not yet seen Season 4, Episodes 1 through 9 of PBS' "Downton Abbey."

Historical accuracy can be tricky to discuss in terms of a period drama, so perhaps "credibility" is a better word. But semantics aside, there are a few aspects of "Downton Abbey" Season 4, that raise some questions, as the period drama attempts to tackle such issues as rape and unwanted childbirth. Huff Post TV spoke to a few historians to get an idea how closely the plot resembles Britain in the 1920s. Here's what we found:

Lady Mary's excessive period of mourning was at least unusual.

University of Leeds historian Dr. Jessica Meyer noted that Mary's behavior was definitely anachronistic, "harking back to Victorian practices which had gone out of style in the years preceding the First World War." Her drawn out impression of a wayward ghost would have been more realistic prior to "criticism of Victoria whose prolonged withdrawal from public life following Albert's death was seen as harmful to British international prestige and influence," says Meyer. Dr. Peter Mandler of the University of Cambridge agreed that "Victorian mourning practices [were] in this period being dumped overboard," adding that, "Remarriage was always acceptable, and quite common."

And she would have had more power over the estate than Lord Grantham lets on.

Although the laws of guardianship were in flux at the time, Meyer notes that Mary would "wield more power as mother of the heir, with legal rights of guardianship, than daughter to Lord Grantham, with the estate entailed away from her." It all depends upon the way in which the estate is entailed. As for Matthew's will, "if his entail provided for an allowance for Mary, she would probably lose it on remarriage."

Anna would have been at much greater risk of being assaulted by the upstairs folk.

When the now-infamous rape episode aired in the U.K., it sparked discussion of whether the scene was necessary, to which creator Julian Fellowes responded it was a historical reality. He's not entirely wrong, but Anna would have been in much more danger of being violated by one of her superiors. Julia Laite, an historian from Birkbeck, University of London, explained that the concept of the "ruined maid" was quite pervasive at the time. Perhaps the most common version of sexual harassment involved "women who were seduced by their masters, convinced into have consensual sex."

And she would have had a solid case, if she chose to go to the police.

To be fair, it seems that Anna primarily chooses to avoid police involvement because she is fearful of Bates' reaction. It is interesting to note that if the rape were to be taken to a court of law, she would have a fantastic case. According to Laite, many rape cases were judged based on behavior. Anna would face no scrutiny in this regard, because her beloved position in the Crawley estate would lend her many character witnesses.

Edith and Michael's marriage scheme makes sense, though she'd be required to become a German citizen.

Men could not divorce women for reason of incurable insanity and women could only divorce their husbands, if they were able to prove they had been excessively beaten. Laite said that it would not have been until the Matrimonial Causes Act of 1937 that things like adultery would be grounds for divorce. Unlike British civil code, German law did allow for divorce on the grounds of incurable insanity, however, it would have required both Michael and Edith to become German citizens, which is a important issue considering the prominence of nationalism at the time.

Although the London train ticket wouldn't be enough to convict Bates, it could have potentially raised a case against him.

Lady and Mrs. Hughes spend quite a bit of time deliberating what they ought to do with the London train ticket found in Bates' coat pocket, and their reactions are not overly dramatized. They suspect that he is lying about his trip to London because he is responsible for Mr. Green's mysterious death -- he was pushed into the street. Mandler says the key point is that "Bates denied he had been in London that day. So the ticket is prima facie evidence that he is lying -- and then this does raise further suspicion." Laite notes that thought it might not have been enough to convict him, it would have been enough to raise him as a suspect.

Generally speaking, servants are far too close with the folks upstairs.

''The relationship they have with their employers is totally wrong," historian Jennifer Newby told The Telegraph. "There was one butler who said that even if in a moment of weakness an employer could ask for advice they wouldn't give it because it could be held against them" -- an observation which paints a far different picture from the cavorting we've seen across the series.