Zinoviev was unwell and feverish. He was told he was to be transferred to another cell. But when he saw the guards he at once understood. All accounts agree that he collapsed, yelling in a high-pitched voice a desperate appeal to Stalin to keep his word. He gave the impression of hysteria, but this is probably not fair, as his voice was always very piercing when he was excited, and he was perhaps trying to make a last speech. He was, in addition, still suffering from heart and liver trouble, so that some sort of collapse is understandable.
1968, Robert Conquest, “Old Bolsheviks Confess”, in The Great Terror: Stalin's Purge of the Thirties, Macmillan Company, page 117