The performer and an assistant engage throughout the performance in a dialogue which more and more exasperates the assistant because the performer grabs all the glory. Eventually, the assistant takes up a sword, shoves it through the performer's torso, and then gloats and basks in the acclaim of the spectators. But the performer, after staggering about a bit, recovers, pulls out the sword (suitably bloodstained), taps the assistant on the back and completely spoils his day!
The sword is very flexible and not sharp, especially along the edges. The performer is wearing under his outfit a metal scabbard which is open at both ends: it is curved and attached to the side of his body. The sword goes into the scabbard at the front, is guided around the performer's body, and emerges at the back. Inside the scabbard is some bloody liquid.
In fact, the assistant could stab the performer in the back for greater effect; but it's much more difficult to do it this way. That's because the performer, when first stabbed, naturally clutches his side where the sword has punctured him: in doing so he makes sure the point is firmly placed in the entrance to the scabbard. While the sword must be flexible, it must not be whippy, or else it may give the game away.