Magnetic insulators have become the prototypes of choice to study quantum critical points (QCPs). In contrast to field-induced quantum phase transitions, pressure-induced criticality is very different. Recently, we observed a rich P-T phase diagram with helimagnetic and collinear magnetic structures in the spin liquid material PHCC, by the use of muon spin rotation. We now propose to start investigating systematically the associated spin dynamics by inelastic neutron scattering. In particular, we intend to measure the dispersion along high symmetry directions of the reciprocal lattice and to determine the incommensurate gap-softening wavevector.