  We discuss the implications of a gauged Abelian hidden-sector communicating
with the Standard Model (SM) fields via kinetic mixing with the SM hypercharge
gauge field, or via the Higgs quartic interaction. We discuss signatures of the
hidden-sector gauge boson at the LHC in the four-lepton channel. We show that a
hidden-sector fermion can be a natural dark-matter candidate with the correct
relic-density, discuss direct-detection prospects, and show how Higgs
signatures may be altered at the LHC.
