The Cool/Lam novels began with The Bigger They Come (also published as Lam to the Slaughter) in 1939. In this novel, Donald Lam has yet to join Bertha Cool's detective agency. Small, frail, and irresistibly attractive for women, Lam is the opposite of the obese and menacing Cool. Between her heavy-handed investigation and his analysis of clues, they work their way through a series of funny and wellplotted mysteries, ending with All Grass Isn't Green in 1970. While not as popular as the Perry Mason novels, the Cool/Lam novels have a large and devoted following.

Bats Fly at Dusk is the seventh in a series of twenty-nine books about Bertha Cool and Donald Lam, all written under the pen name A. A. Fair.

Others in the series are The Bigger They Come, 1939 (also published as Lam to the Slaughter); Turn on the Heat, 1940; Gold Comes in...