  The presence of a quantum critical point separating two distinct
zero-temperature phases is thought to underlie the `strange' metal state of
many high-temperature superconductors. The nature of this quantum critical
point, as well as a description of the resulting strange metal, are central
open problems in condensed matter physics. In large part, the controversy stems
from the lack of a clear broken symmetry to characterize the critical phase
transition, and this challenge is no clearer than in the example of the
unconventional superconductor CeCoIn$_5$. Through Hall effect and Fermi surface
measurements of CeCoIn$_5$, in comparison to ab initio calculations, we find
evidence for a critical point that connects two Fermi surfaces with different
volumes without apparent symmetry-breaking, indicating the presence of a
transition that involves an abrupt localization of one sector of the charge
degrees of freedom. We present a model for the anomalous electrical Hall
resistivity of this material based on the conductivity of valence charge
fluctuations.
