  We adapt the dual-null foliation to the functional Schr\"odinger
representation of quantum field theory and study the behavior of quantum probes
in plane-wave space-times near the null-singularity. A comparison between the
Einstein-Rosen and the Brinkmann patch, where the latter extends beyond the
first, shows a seeming tension that can be resolved by comparing the
configuration spaces. Our analysis concludes that Einstein-Rosen space-times
support exclusively configurations with non-empty gravitational memory that are
focussed to a set of measure zero in the focal plane with respect to a
Brinkmann observer. To conclude, we provide a rough framework to estimate the
qualitative influence of back-reactions on these results.
