  CeRhIn$_{5}$ is a Kondo-lattice prototype in which a magnetic field
B$\bf{^{\ast}\simeq}$ 30 T induces an abrupt Fermi-surface (FS) reconstruction
and pronounced in-plane electrical transport anisotropy all within its
antiferromagnetic state. Though the antiferromagnetic order at zero field is
well-understood, the origin of an emergent state at B$^{\ast}$ remains unknown
due to challenges inherent to probing states microscopically at high fields.
Here, we report low-temperature Nuclear Magnetic Resonance (NMR) measurements
revealing a discontinuous decrease in the $^{115}$In formal Knight shift,
without changes in crystal or magnetic structures, of CeRhIn$_{5}$ at fields
spanning B$^{\ast}$. We show that the emergent state above B$^{\ast}$ results
from a change in Ce's 4f orbitals that arises from field-induced evolution of
crystal-electric field (CEF) energy levels. This change in orbital character
enhances hybridisation between the 4f and the conduction electrons (c.e.) that
leads ultimately to an itinerant quantum-critical point at B$\bf{_{c0} \simeq}$
50 T.
