  The planetary nebula (PN) IC 4997 is one of a few rapidly evolving objects
with variable brightness and nebular emission around a hydrogen-deficient star.
In this study, we have determined the physical conditions and chemical
abundances of this object using the collisionally excited lines (CELs) and
optical recombination lines (ORLs) measured from the medium-resolution spectra
taken in July 2014 with the FIbre-fed \'Echelle Spectrograph on the Nordic
Optical Telescope at La Palma Observatory. We derived electron densities of
$\gtrsim 3 \times 10^4$ cm$^{-3}$ and electron temperatures of $\gtrsim 14,000$
K from CELs, whereas cooler temperatures of $\sim 11,000$ and $\sim 7,000$ K
were obtained from helium and heavy element ORLs, respectively. The elemental
abundances deduced from CELs point to a metal-poor progenitor with
[O/H]$\lesssim-0.75$, whereas the ORL abundances are slightly above the solar
metallicity, [O/H]$\approx 0.15$. Our abundance analysis indicates that the
abundance discrepancy factors (ADFs$\equiv$ORLs/CELs) of this PN are relatively
large: ADF(O$^{2+})\gtrsim 8$ and ADF(N$^{2+})\gtrsim 7$. Further research is
needed to find out how the ADFs and variable emissions are formed in this
object and whether they are associated with a binary companion or a very late
thermal pulse.
