Isabel Ostrander (1883-1924) was a prolific American author who also wrote under the names of Robert Orr Chipperfield, David Fox and Douglas Grant. Some of her books can be downloaded free from Project Gutenberg.  Her final book was completed by pulp writer Christopher Booth who also contributed stories and serials for the Street & Smith detective story magazines.

Bibliography

At One-Thirty (1915)

The Crevice  [with William J. Burns] (1915)

   aka The Lawton Mystery

The Heritage of Cain (1916)

The Clue in the Air (1917)

Island of Intrigue (1918)

Suspense (1918)

Ashes to Ashes (1919)

The Twenty Six Clues (1919)

How Many Cards? (1920)

The Crimson Blotter (1921)

The Tattooed Arm (1922)

McCarty, Incog. (1922)

Annihilation (1924)

Dust to Dust (1924)

Liberation (1924)

  aka Impulse 

The Black Joker (1925)

The Neglected Clue (1925)

The Sleeping Cat (1926)

The Mathematics of Guilt (1926)

The Sleeping Cop (1927) (published posthumously, completed by Christopher B. Booth)

   aka The Braddigan Murder

As Robert Orr Chipperfield

The Second Bullet (1919)

Unseen Hands (1920)

The Man in the Jury Box (1921)

The Trigger of Conscience (1921)

Above Suspicion (1923)

Bright Lights (1924)

As David Fox

The Man Who Convicted Himself (1920)

Ethel Opens the Door (1922)

The Doom Dealer (1923)

The Handwriting on the Wall (1924)

As Douglas Grant

(These are strictly westerns and not detective novels)

The Fifth Ace aka The Red Glove (1918)

Booty (1919)

The Single Track (1919)

Anything Once (1920)

Two-Gun Sue (1922)