Green for Danger — Christianna Brand

An English military hospital, frantically coping with the onslaught of the blitz, discovers it must contend with another more cunning enemy within. While sirens scream and Nazi bombers roar overhead and wreak havoc outside, an insidious terror grips the staff inside as a very subtle murder is committed on the operating table--in full view of seven people. Inspector Cockrill, confined to the hospital by yet another air raid, must duel with a ruthless and clever killer waging his own private war....