(The transmigration of souls, or reincarnation. A rather clumsy application of the concept here, but what the heck, magic isn't about erudition).
An elaborate set is presented: the focal point is a suit of armour. An assistant comes in and dusts and tidies up; he takes the suit of armour apart and puts it back together as part of the process. As he moves away, the suit comes to life, starts knocking him about, chases him all over the stage, and then goes back to its original location in the set. The terrified assistant drags in the performer to show him, but the suit is by now inanimate again, as the performer demonstrates by taking it apart again. The act ends with the performer jeering and booting the assistant off the stage.
This illustration is to give an idea of an elaborate set: certain features are essential, as outlined below, but otherwise let the imagination run loose!
The important features of the set are: B, B: diagonally-placed wings of scenery, or curtains, or whatever C: steps up to the scene
E1, E2, E3, E4: the walls around the scene. Somewhere along E4 is a secret entrance that is big enough to pass the suit of armour.
I, H: two identical suits of armour are placed here: I is behind E1. F: the heart of the trick: a large mirror, mounted so that it can be slid silently, smoothly, and quickly in and out of the set:
G: is where the mirror is when it's out of the set.
The two suits of armour I and H are so placed that I is reflected in the mirror when it's in the scene.
At the start of the act, the mirror is out of the set, and the assistant cleans up the suit at H. When he moves around and approaches I, the mirror is slipped into the scene; another assistant, dressed in an identical suit, comes in through the secret entrance in E4, removes the suit at H and stands there himself. The mirror is then slipped out and the second assistant (at H) animates and starts beating on the first assistant. While the first assistant is off-stage, the second goes back to H and becomes immobile. When the first assistant and the performer come back on to the stage, thereby distracting attention, the mirror is rolled back into the scene, allowing the exit of the second assistant and the re-placement of the second suit of armour. The glass is then rolled out again and the performer dismantles the second suit and humiliates the assistant further.
The mirror mounting must be absolutely silent and obstruction-free, and must be at the same time large and sturdy enough to support the mirror without wobbles or slanting. Therefore, the two pieces of scenery B must be tall enough to conceal the mirror.
As the mirror moves in and out, it would seem that its edge would be momentarily visible. This is obscured by the position of the assistant and of the performer and by appropriate lighting, but above all by the preparation of the mirror.
The silver backing of the mirror is etched with vertical lines: very close together at the edge of the mirror that actually goes into the set, and regularly increasing in distance apart until the silver is unbroken. Thus the reflection will only gradually appear or disappear when the mirror is moved. The width of the lines will have to be determined by experiment.
Point I must be carefully determined so that the reflection of the suit of armour at that point exactly coincides with the position H. There must be marks on the floor at H to indicate the exact position of the assistant and the second suit of armour.
Other scenarios can be implemented with this setting: a painting suddenly coming to life, for instance.