  By exploiting the freedom in defining the dual of spinors, we report an
unexpected theoretical discovery of a quantum field theory of spin-half bosons.
It fulfils Dirac's 1969-70 observation that "there must be boson variables
connected with electrons." The theory is local, Lorentz-invariant, and has a
positive-definite Hamiltonian. We formulate the unitarity-preserving scattering
theory to accommodate the new dual and the associated adjoint. A model of
Yukawa interaction with spin-half bosons and fermions of equal masses is
studied to explicitly show unitarity.
