  The observed neutrino flux can be as a whole well fitted by a simple
power-law of the neutrino energy $E_\nu$, $E_\nu^{-\gamma_\nu}$ ($\gamma_\nu
\simeq 2$). As a notable feature of the spectrum, however, it has a gap between
500 TeV and 1 PeV. Although the existence of the gap in the neutrino spectrum
is not statistically significant at this point, it is very enticing to ask
whether it might hint some physics beyond the Standard Model. In this paper, we
investigate a possibility that the gap can be interpreted as an absorption line
in the power-law spectrum by the cosmic neutrino background through a new
resonance in the MeV range. We also show that the absorption line has rich
information about not only the MeV scale new particle but also the neutrino
masses as well as the distances to the astrophysical sources of the high energy
neutrinos. Viable models to achieve this possibility are also discussed.
