I had never heard of Maurice Level (the pseudonym of Jeanne Mareteux-Level) before tonight, but after reading a couple of his short stories and a few critques of his work in general, I shall have to find more of his stories.
Level was a French writer known for his macabre stories, which were sometimes staged in the renown Theater of the Grand Guignol. Wikipedia says this about him:
“…Level’s short stories may be weak in characterization and motivation, but they are strong on obsession and violence. Their surprise endings are reminiscent of the stories of Guy de Maupassant. Many of Level’s stories were translated into English in the magazine Weird Tales.  As editor John Robert Colombo noted in Stories of Fear and Fascination (2007), Battered Silicon Dispatch Box French critics see Level as the heir of the Symbolist writer Villiers de l’Isle-Adam; British critics, as the successor of Edgar Allan Poe; American critics, as the contemporary of H. P. Lovecraft. Of this fiction, Lovecraft himself observed in Supernatural Horror in Literature (1945), “This type, however, is less a part of the weird tradition than a class peculiar to itself–the so-called conte cruel, in which the wrenching of the emotions is accomplished through dramatic tantalizations, frustrations, and gruesome physical horrors.” Critic Philippe Gontier wrote, “We can only admire, now almost one hundred years later, the great artistry with which Maurice Level fabricated his plots, with what care he fashioned all the details of their unfolding and how with a master’s hand he managed the building of suspense.” Level’s stories, with their gratuitous acts and mindless brutality, may be seen as precursors of “thriller” fiction and “slasher” films.”
A few of Level’s works can be found on the Internet. I read two tonight: “Under the Red Lamp” and “Last Kiss”. They are quite brief and quite terrifying. In my view, the Wikipedia article above provides a good assessment of what I have read so far. Level begins a story with a first sentence that grabs your attention, then sustains the mystery throughout the tale, until you reach a sudden, horrifying, denouement.
I highly recommend investigating his works when you have the time. He is an excellent writer that deserves more recognition than he has.
Here are a few places to start:
“The Last Kiss” at Moonlightstories.magick7.com A husband, blinded and hideously deformed when his wife threw vitriol in his face after he threatened to leave her, intervenes on her behalf when the case comes to court, preventing her from receiving a long jail sentence. At his request she pays him an emotional visit in which she begs his forgiveness and somehow even manages to kiss him, whereupon … Well, not for nothing is Level feted as a master practitioner of the conte cruel. (Synopsis from vaultofevil.proboards.com)
“In the Light of the Red Lamp” at amalgamatedspooks.com “In the first shock of grief, you sometimes have extraordinary ideas … can you believe that I photographed her lying on her deathbed? I took my camera into the white, silent room, and lit the magnesium wire. Yes, overwhelmed as I was with grief, I did with the most scrupulous precaution and care things from which I should shrink today, revolting things … yet it is a great consolation to know she is there, that I shall be able to see her again as she looked that last day.” Now, six months after his beloved’s death, accompanied by the narrator he prepares to develop the photographs of the dead woman. Slowly the images appear – and a horrible tragedy is revealed. (Synopsis from vaultofevil.proboards.com)
“The Grip of Fear” at Google Books (I haven’t read this yet, but it looks interesting.)
Apparently, many of his works are still available only in French, but some (notably those mentioned above) are available in English. His better known works are: Those who Return, Tales of Mystery and Horror, Tales of the Grand Guignol, Les Portes de L’Enfer, The Grip of Fear, and L’Epouvante.