Who killed Sean Regan?

A host of others, smiling killers and gruesome butlers, stalk through the dark,rainy landscape of the film like wraiths. The Big Sleep [1946] is something other than a detective story, with the drive toward rationality that designation is supposed to represent. It is a carnival of criminality, its underworld supernumeraries crowing the film not so much as picturesque character bits, but as tiny, finely-drawn portrayals of deceit and self-interest in a tapestry of meanness.

—Kevin Hagopian, Film Noir Reader 4, p. 42