  Interpretations of searches for the Higgs boson are governed by
model-dependent combinations of Higgs production cross sections and Higgs
branching ratios. Mixing of the Higgs doublet with a hidden sector captures
modifications from the Standard Model Higgs phenomenology in the standard
search channels in a representative way, in particular because invisible Higgs
decay modes open up. As a consequence, LHC exclusion bounds, which disfavor a
heavy Standard Model Higgs can be consistently understood in terms of a
standard-hidden mixed Higgs system. Shedding light on the possible existence of
such an admixture with a hidden sector and quantifying the resemblance of an
eventually discovered scalar resonance with the Standard Model Higgs crucially
depends on measurement of invisible decays. This task will already be tackled
at LHC, but eventually requires the clean environment of a future linear
collider to be ultimately completed.
