  The mass dimension one fermionic field associated with Elko satisfies the
Klein-Gordon but not the Dirac equation. However, its propagator is not a
Green's function of the Klein-Gordon operator. We determine the operator in
which the associated Green's function is the propagator of the fermionic field.
The field is still of mass dimension one, but the obtained Lagrangian resolves
the last outstanding issue of mass dimension one fields. This Lagrangian does
not admit local gauge invariance. Therefore, the mass dimension one fermions
have limited interactions with the Standard Model particles and are natural
dark matter candidates.
