In The Canaris Conspiracy Manvell and Fraenkel tell, how his cell door was permanently open, and the light burned continually, day and night. He was given only one third of the normal prison rations, and as the winter set in his starved body suffered cruelly from the cold. Occasionally he was humiliated by being forced to do menial jobs, such as scrubbing the prison floor, the SS-men mocking him.

On 7 February 1945 Wilhelm Canaris was brought to the Flossenburg concentration camp but he was still ill-treated and often endured having his face slapped by the SS guards. For months he baffled the SS-interrogators with one ruse after another, and he denied all personal complicity in the conspiracy. He never betrayed his fellow participants in the Resistance Movement.

One of Canaris' fellow conspirators, Fabian von Schlabrendorff, later recalled with some amazement: "His skill in acting a part, his cunning, his imagination, the ease with which he affected naive stupidity and then emerged into the most subtle reasoning disarmed the security agents who interrogated him."

Bun on the afternoon of April 5, 1945, Adolf Hitler gave the order: Canaris, Oster and the other conspirators were to be hanged.

In the closing days of World War II, in the gray morning hours of April 9, 1945, gallows were erected hastily in the courtyard. Canaris, pastor Dietrich Bonhoeffer, Major General Hans Oster, Judge Advocate General Carl Sack, Captain Ludwig Gehre - all were ordered to remove their clothing and were led down the steps under the trees to the secluded place of execution before hooting SS guards. Naked under the scaffold, they knelt for the last time to pray - they were hanged. The bodies were taken outside and cremated on a huge bonfire.

Von Schlabrendorff was told by one of the guards that Canaris died slowly and horribly - he took half an hour to die. Two weeks later - on April 23, 1945, - the camp was liberated by American troops.

One of Canaris' fellow-prisoners, the Danish Colonel Lunding, former Director of Danish Military Intelligence, was imprisoned in the cell next to Canaris. He had contact with Canaris shortly before he watched the naked figure of the Admiral being led to execution. Through tapping on the wall of his cell Canaris send his final message to posterity: