The process e$^+$e$^- \rightarrow$~e$^+$e$^-$Z$/\gamma^*$ 
is studied with the OPAL detector at LEP 
at a centre of mass energy of $\sqrt{s} = 189$~GeV.
The cross-section times the branching ratio of the 
Z/$\gamma^*$ decaying into hadrons is measured 
within Lorentz invariant kinematic limits to be 
$(1.2 \pm 0.3 \pm 0.1)$~pb for 
invariant masses of the hadronic system between
$5$~GeV and $60$~GeV and
$(0.7 \pm 0.2 \pm 0.1)$~pb for  hadronic masses above 60~GeV.
The differential cross-sections of the Mandelstam variables 
$\hat{s}$, $\hat{t}$, and $\hat{u}$ are measured 
and compared with the predictions from the Monte Carlo 
generators grc4f and PYTHIA. 
From this, based on a factorisation ansatz, 
the total and differential cross-sections
for the subprocess e$\gamma \rightarrow$~eZ/$\gamma^*$ 
are derived.