  In this paper we study the scattering of massive fermions off of smooth,
spherically symmetric monopoles in $4d$ $SU(2)$ gauge theory. We propose a
complete physical picture of the monopole-fermion interaction which encompasses
all angular momentum modes. We show that as an in-going fermion scatters off a
monopole, it excites trapped $W$-bosons in the monopole core by a version of
the Witten effect so that the monopole can accrue charge and transform into a
dyon at parametrically low energies. The imparted electric charge is then
protected from decay by an emergent $\mathbb{Z}_N$ generalized global symmetry,
creating a stable dyon. At sufficiently low energies, the scattered fermion can
be trapped by the dyon's electrostatic potential, forming a bound state, which
can decay into spherically symmetric fermion modes subject to the preserved
$\mathbb{Z}_N$ global symmetry. We propose that monopole-fermion scattering can
be described in this way without needing to add ``new'' states to the Hilbert
space, thereby eliminating a long standing confusion in the Callan Rubakov
effect.
