In the spring of 1918. On the battlefields of France, a mammoth German offensive threatens the English army with defeat. In England itself, a beleaguered government and panic-stricken, vengeful public seek scapegoats. Two groups are targeted for persecution and prosecution: pacifists and homosexuals. Many are jailed, others lead dangerous double lives; and "the eye in the door" becomes a symbol of the paranoia that threatens to destroy the very fabric of British society. Central to this novel is Lieutenant Billy Prior, recently released from treatment for shell shock by psychiatrist Dr. William Rivers. Prior is in London, assigned to a domestic Intelligence unit. His position demands that he investigate an imprisoned female pacifist accused of plotting a political assassination - a woman who raised him as a child, and who now accuses him of betraying that childhood. At the same time, he has had a casual but intense sexual encounter with a fellow patient of Dr. Rivers - Charles Manning, an upperclass officer whose social status and battlefield wounds must shield him from the growing danger of his exposure as a homosexual. Billy Prior is the man in the middle: a child of the working class raised to the rank of officer and gentleman; a soldier scarred by the horror of war but loyal to the men in the trenches; a bisexual of omnivorous appetites and withered emotions; and above all, a human being who feels himself torn in two as he is asked to take sides.