  We prove global in time dispersion for the wave and the Klein-Gordon equation
inside the Friedlander domain by taking full advantage of the space-time
localization of caustics and a precise estimate of the number of waves that may
cross at a given, large time. Moreover, we uncover a significant difference
between Klein-Gordon and the wave equation in the low frequency, large time
regime, where Klein-Gordon exhibits a worse decay that the wave, unlike in the
flat space.
