The film was based on a book of the same name by Morris L West. If any one can find a copy, perhaps there may be some more detailed explanation of the 'shoes' reference in the Intro' or dedication?

I imagine it comes from linking the quote "Come, follow me," Jesus said, "and I will make you fishers of men." with:

To step into another man's shoes. To take the office or position previously held by another.

“ `That will do, sir,' he thundered, `that will do. It is very evident now what would happen if you stepped into my shoes.”- Good Words, 1887.