Margaret Wetherby Williams (1901-1984) wrote twenty-one mystery novels, published from 1938-1978, under the pseudonym Margaret Erskine.Whether she deliberately chose the Erskine pseudonym as a nod to one of the mistresses of James V of Scotland, I haven't a clue, but I do think both names have a nice authorial ring to them.
Though born in Ontario, she was reared in Devon,a county in southwestern England known for its spectacular scenery and its rich atmosphere.Devonshire is home to Dartmoor,primary setting for Sir Arthur Conan Doyle's The Hound of the Baskervilles. I think growing up in such an atmospherically rich area definitely influenced Erskine's detective fiction because there is often an air of spookiness to both her settings and her plots. When her books were reprinted in paperback in the US in the 1960s and 1970s, they were published by Ace, known for its "Gothic" suspense novels, and indeed they were marketed as such, rather than as detective stories. Bantam later reprinted a number of them as detectives stories.
Her series character was Inspector Septimus Finch, seventh son of a seventh son. A tall man with a surprisingly high voice, Finch always seems to relish the odd circumstances in which he finds himself. If you enjoy old-fashioned mysteries set in eerie houses (I love them myself), then you'll find a lot to enjoy in Erskine's novels.