By 1944 he began human trials of his formula, setting up a secret lab and torture chamber in the hills near an Allied occupied location in Europe. His victims were put to the limits of human endurance pain, but none survived and Dr. Agony had Tula dispose of the bodies. When Mr. Morley—an administrator of Allied occupation in Europe—was captured by Dr. Agony while on a walk, it attracted the attention of Captain America and Bucky who began searching for Morley.
As Agony experimented on Morley, Tula was sent to dispose of his last victim. Tula was spotted by Cap and Bucky and were attacked by the big cat. The pair were able to fight off the big cat and followed its trail. They walked right into a trap door set by Dr. Agony. Before the two heroes could react, they were subjected to Tula's hypnotic purring. Deciding to test on the two heroes, Agony strapped Bucky to a table to begin operating on him first. Captain America, through will power, managed to stomp on Tula's tail causing the cat to howl and pain and stop purring allowing him to break free from the big cat's hold and attack Dr. Agony.
Agony however was prepared for such an attack and dropped a specially designed cage on Captain America. Using the heat elements attached to the bars, Dr. Agony increased the temperature to test Captain America's endurance to heat. While distracted by this, Agony was unable to stop Bucky from breaking free and turning off the heat. While attempting to subdue Bucky, Dr. Agony was unable to prevent Captain America to break out of the cage.
Tula then jumped Captain America, and while the hero struggled with the big cat he struck a light switch. The bright light blinded and disorientated the cat causing it to attack its own master. Dr. Agony was forced to stab his beloved pet to death to try and save himself, however his wounds proved fatal and he bled to death.