In a letter (#259) to H.P. Lovecraft, ca. September or October 1933 Howard tells him about his journey into detective stories:

Lately I’ve been trying to write detective yarns, something entirely new for me, and haven’t had much success — in fact none, so far, except for a short yarn, “Talons in the Dark”, written in San Antonio last spring, and which Kline, as my agent, sold to a magazine called Strange Detective Stories. Kline has been a big help in teaching me the technique of detective story writing; whether I am able to profit by his teaching remains to be seen. (Kline marketed another yarn for me since I wrote the above.)

The other story mentioned is probably this one, published as “The Tomb’s Secret.”