Hello. You did not enter the text to which this question refers, which makes it impossible for it to be answered. However, I will try to help you in the best possible way.
It is only possible to answer your question exactly by reading the text. However, if Helfer knows how to perform a trick with a fly, revealing that trick does not benefit Helfer, since it removes all the mystery of the trick, leaving it dull and without anything that is impressive, that is, revealing the secret of the trick destroys the trick and this is not beneficial.
