In the scene where Herbert and Dan re-animate the dead corpse, watch closely when Herbert rams the little buzz saw into the corpse's chest. At the bottom of the screen, you can see where the fake chest ends.
Based only very loosely on the story "Herbert West: Reanimator" by H.P. Lovecraft, taking great liberties with the original story. This was, reportedly, one of Lovecraft's least favorite among his stories, one that he only wrote in order to "pay the bills."