Metamorphosis (The Substitution Trunk)
When Houdini and his wife Bessie went on in the road in 1894, they featured an illusion called "Metamorphosis." While other magicians performed this illusion, it was the use of both a man and a woman that made it so successful. It was this trick that gained the Houdini's their first big tour with the Welsh Brothers Circus in 1895. In this trick, Houdini's hands would be fastened behind his back as he was placed inside a large bag which was knotted closed. He was then placed inside a large box, which was locked and strapped closed. The box is then placed inside a cabinet. Mrs. Houdini would then draw the curtain closed and clap three times. At the third clap, Houdini himself would draw open the curtain and Mrs. Houdini would be gone. When the box is opened, Mrs. Houdini is found inside the bag with the knots and seals unbroken and her hands secured in exactly the same way as her husband's.
The answer to this trick begins with the binding of Houdini's wrists. He was an expert at freeing himself from ropes and ties, especially those in which the knots could be slipped and tightened later. He would simply free himself from the ropes as the bag was being raised above his head. The audience could not see this, as his hands were purposefully bound behind his back. The rope used to secure the sack itself ran through a series of metal eyelets around the upper edge of the bag, so the rope would be both inside and outside of the bag. Houdini merely needed to pull on the rope from the inside of the bag to open the sack. The box or trunk was over-sized, allowing for more freedom of movement. It had a rear panel opening inward with a release on the inside. Having gotten himself free from both the rope and the sack, Houdini would wait for the curtain to drop. As the curtain falls, he simply uses the release and trap panel to exit the box. Contrary to the audience's assumption, it was Houdini himself who was doing the clapping, as Bessie got inside the box through the open back panel.
Harry would then appear from behind the curtain. When Harry opened the curtain, Bessie was already inside the box. Once inside, she closed the panel, slid into the wrist restraints, left slack by Harry and pulled the sack over her. Inside the sack, she would use the inner loop system to pull the knot tight at the top of the bag. All of this work was performed as Harry went through the motions of unlocking the box.