A short story/novelette with echoes of Edgar Allan Poe's "The Fall of the House of Usher" and Henry James's novel The Turn of the Screw--but more spookier and more "horrifying" than either.
The ending left a lot of the questions unanswered. But I liked the atmosphere, mystery, and the third person narrative voice, which felt very much like a candid first person narration. The writing style isn't as strong as Kelly Robson's new novel High Times in the Low Parliament (which is the reason I was led to the short story--I wanted to read more of her writing), but for a short story it works well.
I was fascinated by the characters, both the protagonist and the nursery maid (the kid's a little disturbing and, if I may use the word, disgusting). I wish we'd seen more of Herr Lambrecht--he was by far the most intriguing and complex character, with a lot of unexplored potential. It's a pity the short fiction format didn't leave a lot of space for him...
That, combined with the ambiguous, unexplained ending, makes me think the story could've been much more interesting with a little more length.