Some twisted sectors for the Moonshine Module

For the moonshine module $V^{\natural},$ whose automorphism is the Monster ${\Bbb M},$ We show how to give a uniform existence proof for irreducible $g$-twisted modules for elements of type $2A,$ $2B$ and $4A$ in ${\Bbb M}.$ The most interesting of these is the twisted sector $V^{\natural}(2A),$ whose automorphism group is essentially the centralizer of $2A$ in ${\Bbb M}.$ This is a 2-fold central extension of the Baby Monster, the second largest sporadic simple group. We also establish uniqueness of the twisted sectors and the hauptmodul property for the graded traces of automorphisms of odd order, as predicted by conformal field theory.