  The pion and nucleon mass differences generate a very pronounced cusp in the
photoproduction reaction of a single pion on the nucleon. A nonrelativistic
effective field theory to describe this reaction is constructed. The approach
is rigorous in the sense that it is an effective field theory with a consistent
power counting scheme. Expressions for the S- and P-wave multipole amplitudes
for all four reaction channels at two loops are given.
