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The play was not officially a Ruthven play in the original French version written in 1865. But it's clearly drawing on the earlier French Ruthven plays, so the Translator (Frank Morlock) chose to take some artistic license.
The play gives it's Vampire an Eastern European background. That seems standard to us today, but among French and English 19th Century Ruthven and quasi Ruthven plays that all seem to have a 17th century Scotland fetish (due to Ruthven being a Scottish name) this is the only one I can think of. This Vampire clams to be the heir to a Scottish noble house through his mother, but his father was a Moldovian count.
It fits the usual Ruthven play pattern in that the lead of the play becomes an unwitting accomplice of The Vampire, knowing what he is but being for some reason unwilling or unable to warn anyone as The Vampire proceeds to target his Sister and/or Love interest.
I actually think it was unnecessary to make this name change of Douglas to Ruthven to imagine it being Ruthven (or any other more well known Vampire), because I feel it highly probable that The Vampire is NOT who he's claiming to be, and so his true name is never reveled at all.
It anticipates Dracula in having the Vampire's antagonist be a Doctor, a man of science familiar with the Vampire legend, but unlike Van Helsing and Dr. Stewart this scientist is also a remorseful accomplish of the Vampire. But Dr. Maxwell does follow the tradition of the protagonists of other Ruthven plays going back to Aubrey of Polidori's original story in being a person who becomes aware of his Vampire state and is mostly helpless as the Vampire then targets his Sister and love interest.
The Vampire also has a sort of Hypnotic ability. This was also not a universal trait among Pre-Dracula vampires. I think Stoker took it primarily from Carmilla which is still latter then this. I don't recall it appearing in any other Ruthven plays, not nearly so explicitly anyway.
I read this play months ago and I feel it serves an interesting overlooked stepping stone in the development of Vampire fiction from Lord Ruthven to Count Dracula. It's unlikely that Stoker read it though, since it wasn't available in English back then.
Most shocking, it does provide the only example that I've found Pre-Nosferatu of a reference to Vampires who have to avoid Sunlight. This Vampire doesn't currently have to, rather it's something he's trying to avoid becoming by succeeding in his current plan. An early example of the possibility of there being different kinds or classes of Vampires. Thing is, since I know Morlock is more wiling to take liberties then Stableford, maybe that wasn't in the original version?
Since the BlackCoatPress translation sets a precedent for changing the identity of the title Vampire. I think it could easily work to make another translation, that moves the setting from 1648 Scotland to 1890s London. And replaces the Douglas inheritance the Vampire is after with Carfax. And then...
Dr. Maxwell = Dr. Stewart
Fanny = Mina
Anna = Lucy
Reginald = Johnathon Harker
Sr. William Clifford = Sr. Arthur Holmwood
Dick Thorn = Quincey
Tom Platt = Renfield
And you'd have a script that arguably resembles Stoker's novel more then Horror of Dracula (the first Hammer Dracula film) does. And, Spoiler Alert!!!! Anticipates Scars of Dracula by having The Vampire struck by Lighting at the end.
I'm going now to add my thoughts on the original story Morlock adds.
It's basically a Ruthven origin story, and ties him to the historical Ruthven clan of Scotland. Who were prominent during the reigns of Mary Stuart and James VI of Scotland and I of England.
It's focused on Patrick Ruthven who was behind the Murder of David Rizzio. But it's implied to be his Son who actually becomes The Vampire.
I like how the story starts but not where it ultimately goes.