"Hands down one of the best formal detective stories ever written."— Kirkus Reviews, STARRED reviewThis Golden Age masterclass of red herrings and tricky twists, first published in 1944, features a tense and claustrophobic investigation with a close-knit cast of suspects."You have to reach for the greatest of the Great Names (Agatha Christie, John Dickson Carr, Ellery Queen) to find Christianna Brand's rivals in the subtleties of the trade."—Anthony Boucher in The New York TimesIt is 1942, and struggling up the hill to the new Kent military hospital Heron's Park, postman Joseph Higgins is soon to deliver seven letters of acceptance for roles at the infirmary. He has no idea that the sender of one of the letters will be the cause of his demise in just one year's time.When Higgins returns to Heron's Park with injuries from a bombing raid in 1943, his inexplicable death by asphyxiation in the operating theatre casts four nurses and three doctors under suspicion, and a second death in quic