  It has been shown that the data from the Large Hadron Collider (LHC) does not
rule out a chiral sequential fourth generation of fermions that obtain their
masses through an identical mechanism as the other three generations do.
However, this is possible only if the scalar sector of the Standard Model is
suitably enhanced, like embedding it in a type-II two-Higgs doublet model. In
this article, we try to show that double Higgs production (DHP) can unveil the
existence of such a hidden fourth generation in a very efficient way. While the
DHP cross-section in the SM is quite small, it is significantly enhanced with a
fourth generation. We perform a detailed analysis of the dependence of the DHP
cross-section on the model parameters, and show that either a positive signal
of DHP is seen in the early next run of the LHC, or the model is ruled out.
