  In the context of a left-right symmetric model, we introduce one full
generation of vectorlike lepton doublets (both left and right-handed) together
with their mirror doublets. We show that the lightest vectorlike neutrino in
the model is right-handed, and can serve as the dark matter candidate. We find
that the relic density, as well as the direct and indirect DM detection bounds,
are satisfied for a large range of the parameter space of the model. In
accordance with the parameter space, we then explore the possibility of
detecting signals of the model at both the LHC and the ILC, in the pair
production of the associated vectorlike charged leptons which decay into final
states including dark matter. A comprehensive analysis of signal and
backgrounds shows that the signals at the ILC, especially with polarized beams
are likely to be visible for light vectorlike leptons, even with low
luminosity, rendering our model highly predictable and experimentally testable.
