

nowhere can I find the name of the cover artist

1959 Doubleday hardcover
cover art by Harry Bennett
1960 Boardman hardcover in the UK, below the UK softcover
pseudonym of Aaron Marc Stein
30th with Inspector Schmidt, head of the Manhattan Homicide Squad


pseudonym of Robert (Lee) Martin
1959 Dodd Mead hardcover, this the later 1960 Crest reissue
cover art by Robert McGinnis
better image than previously posted

Stewart Sterling was a pseudonym of Prentice Winchell, who also wrote under four other names.
1951 Dutton hardcover, this the later 1953 Dell reprint
cover art by Bob Hilbert
better image than previously posted