  In the singlet-triplet majoron model of neutrino mass, lepton number is
spontaneously broken. If it is also softly broken, then a naturally light
pseudoscalar particle $\eta_I$ exists. It may then act as a light mediator for
a real singlet scalar $\chi$ with odd dark parity. It is itself unstable, but
decays dominantly to two neutrinos through its triplet scalar component,
thereby not disturbing the cosmic microwave background (CMB). It also mixes
with the standard-model Higgs boson only in one loop, thereby not contributing
significantly to the elastic scattering of $\chi$ off nuclei in dark-matter
direct-search experiments.
